mcs/class/System/System.Net.Mail/SmtpClient.cs

   1 //
   2 // System.Net.Mail.SmtpClient.cs
   3 //
   4 // Author:
   5 //      Tim Coleman (tim@timcoleman.com)
   6 //
   7 // Copyright (C) Tim Coleman, 2004
   8 //
   9
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31 #if SECURITY_DEP
  32
  33 #if MONOTOUCH || MONODROID
  34 using System.Security.Cryptography.X509Certificates;
  35 #else
  36 extern alias PrebuiltSystem;
  37 using X509CertificateCollection = PrebuiltSystem::System.Security.Cryptography.X509Certificates.X509CertificateCollection;
  38 using System.Security.Cryptography.X509Certificates;
  39 #endif
  40
  41 #endif
  42
  43 using System;
  44 using System.Collections.Generic;
  45 using System.ComponentModel;
  46 using System.Globalization;
  47 using System.IO;
  48 using System.Net;
  49 using System.Net.Mime;
  50 using System.Net.Sockets;
  51 using System.Text;
  52 using System.Threading;
  53 using System.Reflection;
  54 using System.Net.Configuration;
  55 using System.Configuration;
  56 using System.Net.Security;
  57 using System.Security.Authentication;
  58 #if NET_4_5
  59 using System.Threading.Tasks;
  60 #endif
  61
  62 namespace System.Net.Mail {
  63         public class SmtpClient
  64         : IDisposable
  65         {
  66                 #region Fields
  67
  68                 string host;
  69                 int port;
  70                 int timeout = 100000;
  71                 ICredentialsByHost credentials;
  72                 string pickupDirectoryLocation;
  73                 SmtpDeliveryMethod deliveryMethod;
  74                 bool enableSsl;
  75 #if SECURITY_DEP
  76                 X509CertificateCollection clientCertificates;
  77 #endif
  78
  79                 TcpClient client;
  80                 Stream stream;
  81                 StreamWriter writer;
  82                 StreamReader reader;
  83                 int boundaryIndex;
  84                 MailAddress defaultFrom;
  85
  86                 MailMessage messageInProcess;
  87
  88                 BackgroundWorker worker;
  89                 object user_async_state;
  90
  91                 [Flags]
  92                 enum AuthMechs {
  93                         None        = 0,
  94                         Login       = 0x01,
  95                         Plain       = 0x02,
  96                 }
  97
  98                 class CancellationException : Exception
  99                 {
 100                 }
 101
 102                 AuthMechs authMechs;
 103                 Mutex mutex = new Mutex ();
 104
 105                 #endregion // Fields
 106
 107                 #region Constructors
 108
 109                 public SmtpClient ()
 110                         : this (null, 0)
 111                 {
 112                 }
 113
 114                 public SmtpClient (string host)
 115                         : this (host, 0)
 116                 {
 117                 }
 118
 119                 public SmtpClient (string host, int port) {
 120 #if CONFIGURATION_DEP
 121                         SmtpSection cfg = (SmtpSection) ConfigurationManager.GetSection ("system.net/mailSettings/smtp");
 122
 123                         if (cfg != null) {
 124                                 this.host = cfg.Network.Host;
 125                                 this.port = cfg.Network.Port;
 126                                 this.enableSsl = cfg.Network.EnableSsl;
 127                                 TargetName = cfg.Network.TargetName;
 128                                 if (this.TargetName == null)
 129                                         TargetName = "SMTPSVC/" + (host != null ? host : "");
 130
 131
 132                                 if (cfg.Network.UserName != null) {
 133                                         string password = String.Empty;
 134
 135                                         if (cfg.Network.Password != null)
 136                                                 password = cfg.Network.Password;
 137
 138                                         Credentials = new CCredentialsByHost (cfg.Network.UserName, password);
 139                                 }
 140
 141                                 if (!String.IsNullOrEmpty (cfg.From))
 142                                         defaultFrom = new MailAddress (cfg.From);
 143                         }
 144 #else
 145                         // Just to eliminate the warning, this codepath does not end up in production.
 146                         defaultFrom = null;
 147 #endif
 148
 149                         if (!String.IsNullOrEmpty (host))
 150                                 this.host = host;
 151
 152                         if (port != 0)
 153                                 this.port = port;
 154                         else if (this.port == 0)
 155                                 this.port = 25;
 156                 }
 157
 158                 #endregion // Constructors
 159
 160                 #region Properties
 161
 162 #if SECURITY_DEP
 163                 [MonoTODO("Client certificates not used")]
 164                 public X509CertificateCollection ClientCertificates {
 165                         get {
 166                                 if (clientCertificates == null)
 167                                         clientCertificates = new X509CertificateCollection ();
 168                                 return clientCertificates;
 169                         }
 170                 }
 171 #endif
 172
 173                 public
 174                 string TargetName { get; set; }
 175
 176                 public ICredentialsByHost Credentials {
 177                         get { return credentials; }
 178                         set {
 179                                 CheckState ();
 180                                 credentials = value;
 181                         }
 182                 }
 183
 184                 public SmtpDeliveryMethod DeliveryMethod {
 185                         get { return deliveryMethod; }
 186                         set {
 187                                 CheckState ();
 188                                 deliveryMethod = value;
 189                         }
 190                 }
 191
 192                 public bool EnableSsl {
 193                         get { return enableSsl; }
 194                         set {
 195                                 CheckState ();
 196                                 enableSsl = value;
 197                         }
 198                 }
 199
 200                 public string Host {
 201                         get { return host; }
 202                         set {
 203                                 if (value == null)
 204                                         throw new ArgumentNullException ("value");
 205                                 if (value.Length == 0)
 206                                         throw new ArgumentException ("An empty string is not allowed.", "value");
 207                                 CheckState ();
 208                                 host = value;
 209                         }
 210                 }
 211
 212                 public string PickupDirectoryLocation {
 213                         get { return pickupDirectoryLocation; }
 214                         set { pickupDirectoryLocation = value; }
 215                 }
 216
 217                 public int Port {
 218                         get { return port; }
 219                         set {
 220                                 if (value <= 0)
 221                                         throw new ArgumentOutOfRangeException ("value");
 222                                 CheckState ();
 223                                 port = value;
 224                         }
 225                 }
 226
 227                 [MonoTODO]
 228                 public ServicePoint ServicePoint {
 229                         get { throw new NotImplementedException (); }
 230                 }
 231
 232                 public int Timeout {
 233                         get { return timeout; }
 234                         set {
 235                                 if (value < 0)
 236                                         throw new ArgumentOutOfRangeException ("value");
 237                                 CheckState ();
 238                                 timeout = value;
 239                         }
 240                 }
 241
 242                 public bool UseDefaultCredentials {
 243                         get { return false; }
 244                         [MonoNotSupported ("no DefaultCredential support in Mono")]
 245                         set {
 246                                 if (value)
 247                                         throw new NotImplementedException ("Default credentials are not supported");
 248                                 CheckState ();
 249                         }
 250                 }
 251
 252                 #endregion // Properties
 253
 254                 #region Events
 255
 256                 public event SendCompletedEventHandler SendCompleted;
 257
 258                 #endregion // Events
 259
 260                 #region Methods
 261                 public void Dispose ()
 262                 {
 263                         Dispose (true);
 264                 }
 265
 266                 [MonoTODO ("Does nothing at the moment.")]
 267                 protected virtual void Dispose (bool disposing)
 268                 {
 269                         // TODO: We should close all the connections and abort any async operations here
 270                 }
 271                 private void CheckState ()
 272                 {
 273                         if (messageInProcess != null)
 274                                 throw new InvalidOperationException ("Cannot set Timeout while Sending a message");
 275                 }
 276
 277                 private static string EncodeAddress(MailAddress address)
 278                 {
 279                         if (!String.IsNullOrEmpty (address.DisplayName)) {
 280                                 string encodedDisplayName = ContentType.EncodeSubjectRFC2047 (address.DisplayName, Encoding.UTF8);
 281                                 return "\"" + encodedDisplayName + "\" <" + address.Address + ">";
 282                         }
 283                         return address.ToString ();
 284                 }
 285
 286                 private static string EncodeAddresses(MailAddressCollection addresses)
 287                 {
 288                         StringBuilder sb = new StringBuilder();
 289                         bool first = true;
 290                         foreach (MailAddress address in addresses) {
 291                                 if (!first) {
 292                                         sb.Append(", ");
 293                                 }
 294                                 sb.Append(EncodeAddress(address));
 295                                 first = false;
 296                         }
 297                         return sb.ToString();
 298                 }
 299
 300                 private string EncodeSubjectRFC2047 (MailMessage message)
 301                 {
 302                         return ContentType.EncodeSubjectRFC2047 (message.Subject, message.SubjectEncoding);
 303                 }
 304
 305                 private string EncodeBody (MailMessage message)
 306                 {
 307                         string body = message.Body;
 308                         Encoding encoding = message.BodyEncoding;
 309                         // RFC 2045 encoding
 310                         switch (message.ContentTransferEncoding) {
 311                         case TransferEncoding.SevenBit:
 312                                 return body;
 313                         case TransferEncoding.Base64:
 314                                 return Convert.ToBase64String (encoding.GetBytes (body), Base64FormattingOptions.InsertLineBreaks);
 315                         default:
 316                                 return ToQuotedPrintable (body, encoding);
 317                         }
 318                 }
 319
 320                 private string EncodeBody (AlternateView av)
 321                 {
 322                         //Encoding encoding = av.ContentType.CharSet != null ? Encoding.GetEncoding (av.ContentType.CharSet) : Encoding.UTF8;
 323
 324                         byte [] bytes = new byte [av.ContentStream.Length];
 325                         av.ContentStream.Read (bytes, 0, bytes.Length);
 326
 327                         // RFC 2045 encoding
 328                         switch (av.TransferEncoding) {
 329                         case TransferEncoding.SevenBit:
 330                                 return Encoding.ASCII.GetString (bytes);
 331                         case TransferEncoding.Base64:
 332                                 return Convert.ToBase64String (bytes, Base64FormattingOptions.InsertLineBreaks);
 333                         default:
 334                                 return ToQuotedPrintable (bytes);
 335                         }
 336                 }
 337
 338
 339                 private void EndSection (string section)
 340                 {
 341                         SendData (String.Format ("--{0}--", section));
 342                         SendData (string.Empty);
 343                 }
 344
 345                 private string GenerateBoundary ()
 346                 {
 347                         string output = GenerateBoundary (boundaryIndex);
 348                         boundaryIndex += 1;
 349                         return output;
 350                 }
 351
 352                 private static string GenerateBoundary (int index)
 353                 {
 354                         return String.Format ("--boundary_{0}_{1}", index, Guid.NewGuid ().ToString ("D"));
 355                 }
 356
 357                 private bool IsError (SmtpResponse status)
 358                 {
 359                         return ((int) status.StatusCode) >= 400;
 360                 }
 361
 362                 protected void OnSendCompleted (AsyncCompletedEventArgs e)
 363                 {
 364                         try {
 365                                 if (SendCompleted != null)
 366                                         SendCompleted (this, e);
 367                         } finally {
 368                                 worker = null;
 369                                 user_async_state = null;
 370                         }
 371                 }
 372
 373                 private void CheckCancellation ()
 374                 {
 375                         if (worker != null && worker.CancellationPending)
 376                                 throw new CancellationException ();
 377                 }
 378
 379                 private SmtpResponse Read () {
 380                         byte [] buffer = new byte [512];
 381                         int position = 0;
 382                         bool lastLine = false;
 383
 384                         do {
 385                                 CheckCancellation ();
 386
 387                                 int readLength = stream.Read (buffer, position, buffer.Length - position);
 388                                 if (readLength > 0) {
 389                                         int available = position + readLength - 1;
 390                                         if (available > 4 && (buffer [available] == '\n' || buffer [available] == '\r'))
 391                                                 for (int index = available - 3; ; index--) {
 392                                                         if (index < 0 || buffer [index] == '\n' || buffer [index] == '\r') {
 393                                                                 lastLine = buffer [index + 4] == ' ';
 394                                                                 break;
 395                                                         }
 396                                                 }
 397
 398                                         // move position
 399                                         position += readLength;
 400
 401                                         // check if buffer is full
 402                                         if (position == buffer.Length) {
 403                                                 byte [] newBuffer = new byte [buffer.Length * 2];
 404                                                 Array.Copy (buffer, 0, newBuffer, 0, buffer.Length);
 405                                                 buffer = newBuffer;
 406                                         }
 407                                 }
 408                                 else {
 409                                         break;
 410                                 }
 411                         } while (!lastLine);
 412
 413                         if (position > 0) {
 414                                 Encoding encoding = new ASCIIEncoding ();
 415
 416                                 string line = encoding.GetString (buffer, 0, position - 1);
 417
 418                                 // parse the line to the lastResponse object
 419                                 SmtpResponse response = SmtpResponse.Parse (line);
 420
 421                                 return response;
 422                         } else {
 423                                 throw new System.IO.IOException ("Connection closed");
 424                         }
 425                 }
 426
 427                 void ResetExtensions()
 428                 {
 429                         authMechs = AuthMechs.None;
 430                 }
 431
 432                 void ParseExtensions (string extens)
 433                 {
 434                         string[] parts = extens.Split ('\n');
 435
 436                         foreach (string part in parts) {
 437                                 if (part.Length < 4)
 438                                         continue;
 439
 440                                 string start = part.Substring (4);
 441                                 if (start.StartsWith ("AUTH ", StringComparison.Ordinal)) {
 442                                         string[] options = start.Split (' ');
 443                                         for (int k = 1; k < options.Length; k++) {
 444                                                 string option = options[k].Trim();
 445                                                 // GSSAPI, KERBEROS_V4, NTLM not supported
 446                                                 switch (option) {
 447                                                 /*
 448                                                 case "CRAM-MD5":
 449                                                         authMechs |= AuthMechs.CramMD5;
 450                                                         break;
 451                                                 case "DIGEST-MD5":
 452                                                         authMechs |= AuthMechs.DigestMD5;
 453                                                         break;
 454                                                 */
 455                                                 case "LOGIN":
 456                                                         authMechs |= AuthMechs.Login;
 457                                                         break;
 458                                                 case "PLAIN":
 459                                                         authMechs |= AuthMechs.Plain;
 460                                                         break;
 461                                                 }
 462                                         }
 463                                 }
 464                         }
 465                 }
 466
 467                 public void Send (MailMessage message)
 468                 {
 469                         if (message == null)
 470                                 throw new ArgumentNullException ("message");
 471
 472                         if (deliveryMethod == SmtpDeliveryMethod.Network && (Host == null || Host.Trim ().Length == 0))
 473                                 throw new InvalidOperationException ("The SMTP host was not specified");
 474                         else if (deliveryMethod == SmtpDeliveryMethod.PickupDirectoryFromIis)
 475                                 throw new NotSupportedException("IIS delivery is not supported");
 476
 477                         if (port == 0)
 478                                 port = 25;
 479
 480                         // Block while sending
 481                         mutex.WaitOne ();
 482                         try {
 483                                 messageInProcess = message;
 484                                 if (deliveryMethod == SmtpDeliveryMethod.SpecifiedPickupDirectory)
 485                                         SendToFile (message);
 486                                 else
 487                                         SendInternal (message);
 488                         } catch (CancellationException) {
 489                                 // This exception is introduced for convenient cancellation process.
 490                         } catch (SmtpException) {
 491                                 throw;
 492                         } catch (Exception ex) {
 493                                 throw new SmtpException ("Message could not be sent.", ex);
 494                         } finally {
 495                                 // Release the mutex to allow other threads access
 496                                 mutex.ReleaseMutex ();
 497                                 messageInProcess = null;
 498                         }
 499                 }
 500
 501                 private void SendInternal (MailMessage message)
 502                 {
 503                         CheckCancellation ();
 504
 505                         try {
 506                                 client = new TcpClient (host, port);
 507                                 stream = client.GetStream ();
 508                                 // FIXME: this StreamWriter creation is bogus.
 509                                 // It expects as if a Stream were able to switch to SSL
 510                                 // mode (such behavior is only in Mainsoft Socket API).
 511                                 writer = new StreamWriter (stream);
 512                                 reader = new StreamReader (stream);
 513
 514                                 SendCore (message);
 515                         } finally {
 516                                 if (writer != null)
 517                                         writer.Close ();
 518                                 if (reader != null)
 519                                         reader.Close ();
 520                                 if (stream != null)
 521                                         stream.Close ();
 522                                 if (client != null)
 523                                         client.Close ();
 524                         }
 525                 }
 526
 527                 // FIXME: simple implementation, could be brushed up.
 528                 private void SendToFile (MailMessage message)
 529                 {
 530                         if (!Path.IsPathRooted (pickupDirectoryLocation))
 531                                 throw new SmtpException("Only absolute directories are allowed for pickup directory.");
 532
 533                         string filename = Path.Combine (pickupDirectoryLocation,
 534                                 Guid.NewGuid() + ".eml");
 535
 536                         try {
 537                                 writer = new StreamWriter(filename);
 538
 539                                 // FIXME: See how Microsoft fixed the bug about envelope senders, and how it actually represents the info in .eml file headers
 540                                 //        For all we know, defaultFrom may be the envelope sender
 541                                 // For now, we are no worse than some versions of .NET
 542                                 MailAddress from = message.From;
 543                                 if (from == null)
 544                                         from = defaultFrom;
 545
 546                                 string dt = DateTime.Now.ToString("ddd, dd MMM yyyy HH':'mm':'ss zzz", DateTimeFormatInfo.InvariantInfo);
 547                                 // remove ':' from time zone offset (e.g. from "+01:00")
 548                                 dt = dt.Remove(dt.Length - 3, 1);
 549                                 SendHeader(HeaderName.Date, dt);
 550
 551                                 SendHeader (HeaderName.From, EncodeAddress(from));
 552                                 SendHeader (HeaderName.To, EncodeAddresses(message.To));
 553                                 if (message.CC.Count > 0)
 554                                         SendHeader (HeaderName.Cc, EncodeAddresses(message.CC));
 555                                 SendHeader (HeaderName.Subject, EncodeSubjectRFC2047 (message));
 556
 557                                 foreach (string s in message.Headers.AllKeys)
 558                                         SendHeader (s, message.Headers [s]);
 559
 560                                 AddPriorityHeader (message);
 561
 562                                 boundaryIndex = 0;
 563                                 if (message.Attachments.Count > 0)
 564                                         SendWithAttachments (message);
 565                                 else
 566                                         SendWithoutAttachments (message, null, false);
 567
 568
 569                         } finally {
 570                                 if (writer != null) writer.Close(); writer = null;
 571                         }
 572                 }
 573
 574                 private void SendCore (MailMessage message)
 575                 {
 576                         SmtpResponse status;
 577
 578                         status = Read ();
 579                         if (IsError (status))
 580                                 throw new SmtpException (status.StatusCode, status.Description);
 581
 582                         // EHLO
 583
 584                         // FIXME: parse the list of extensions so we don't bother wasting
 585                         // our time trying commands if they aren't supported.
 586                         status = SendCommand ("EHLO " + Dns.GetHostName ());
 587
 588                         if (IsError (status)) {
 589                                 status = SendCommand ("HELO " + Dns.GetHostName ());
 590
 591                                 if (IsError (status))
 592                                         throw new SmtpException (status.StatusCode, status.Description);
 593                         } else {
 594                                 // Parse ESMTP extensions
 595                                 string extens = status.Description;
 596
 597                                 if (extens != null)
 598                                         ParseExtensions (extens);
 599                         }
 600
 601                         if (enableSsl) {
 602                                 InitiateSecureConnection ();
 603                                 ResetExtensions();
 604                                 writer = new StreamWriter (stream);
 605                                 reader = new StreamReader (stream);
 606                                 status = SendCommand ("EHLO " + Dns.GetHostName ());
 607
 608                                 if (IsError (status)) {
 609                                         status = SendCommand ("HELO " + Dns.GetHostName ());
 610
 611                                         if (IsError (status))
 612                                                 throw new SmtpException (status.StatusCode, status.Description);
 613                                 } else {
 614                                         // Parse ESMTP extensions
 615                                         string extens = status.Description;
 616                                         if (extens != null)
 617                                                 ParseExtensions (extens);
 618                                 }
 619                         }
 620
 621                         if (authMechs != AuthMechs.None)
 622                                 Authenticate ();
 623
 624                         // The envelope sender: use 'Sender:' in preference of 'From:'
 625                         MailAddress sender = message.Sender;
 626                         if (sender == null)
 627                                 sender = message.From;
 628                         if (sender == null)
 629                                 sender = defaultFrom;
 630
 631                         // MAIL FROM:
 632                         status = SendCommand ("MAIL FROM:<" + sender.Address + '>');
 633                         if (IsError (status)) {
 634                                 throw new SmtpException (status.StatusCode, status.Description);
 635                         }
 636
 637                         // Send RCPT TO: for all recipients
 638                         List<SmtpFailedRecipientException> sfre = new List<SmtpFailedRecipientException> ();
 639
 640                         for (int i = 0; i < message.To.Count; i ++) {
 641                                 status = SendCommand ("RCPT TO:<" + message.To [i].Address + '>');
 642                                 if (IsError (status))
 643                                         sfre.Add (new SmtpFailedRecipientException (status.StatusCode, message.To [i].Address));
 644                         }
 645                         for (int i = 0; i < message.CC.Count; i ++) {
 646                                 status = SendCommand ("RCPT TO:<" + message.CC [i].Address + '>');
 647                                 if (IsError (status))
 648                                         sfre.Add (new SmtpFailedRecipientException (status.StatusCode, message.CC [i].Address));
 649                         }
 650                         for (int i = 0; i < message.Bcc.Count; i ++) {
 651                                 status = SendCommand ("RCPT TO:<" + message.Bcc [i].Address + '>');
 652                                 if (IsError (status))
 653                                         sfre.Add (new SmtpFailedRecipientException (status.StatusCode, message.Bcc [i].Address));
 654                         }
 655
 656                         if (sfre.Count >0)
 657                                 throw new SmtpFailedRecipientsException ("failed recipients", sfre.ToArray ());
 658
 659                         // DATA
 660                         status = SendCommand ("DATA");
 661                         if (IsError (status))
 662                                 throw new SmtpException (status.StatusCode, status.Description);
 663
 664                         // Send message headers
 665                         string dt = DateTime.Now.ToString ("ddd, dd MMM yyyy HH':'mm':'ss zzz", DateTimeFormatInfo.InvariantInfo);
 666                         // remove ':' from time zone offset (e.g. from "+01:00")
 667                         dt = dt.Remove (dt.Length - 3, 1);
 668                         SendHeader (HeaderName.Date, dt);
 669
 670                         MailAddress from = message.From;
 671                         if (from == null)
 672                                 from = defaultFrom;
 673
 674                         SendHeader (HeaderName.From, EncodeAddress (from));
 675                         SendHeader (HeaderName.To, EncodeAddresses (message.To));
 676                         if (message.CC.Count > 0)
 677                                 SendHeader (HeaderName.Cc, EncodeAddresses (message.CC));
 678                         SendHeader (HeaderName.Subject, EncodeSubjectRFC2047 (message));
 679
 680                         string v = "normal";
 681
 682                         switch (message.Priority){
 683                         case MailPriority.Normal:
 684                                 v = "normal";
 685                                 break;
 686
 687                         case MailPriority.Low:
 688                                 v = "non-urgent";
 689                                 break;
 690
 691                         case MailPriority.High:
 692                                 v = "urgent";
 693                                 break;
 694                         }
 695                         SendHeader ("Priority", v);
 696                         if (message.Sender != null)
 697                                 SendHeader ("Sender", EncodeAddress (message.Sender));
 698                         if (message.ReplyToList.Count > 0)
 699                                 SendHeader ("Reply-To", EncodeAddresses (message.ReplyToList));
 700
 701                         foreach (string s in message.Headers.AllKeys)
 702                                 SendHeader (s, ContentType.EncodeSubjectRFC2047 (message.Headers [s], message.HeadersEncoding));
 703
 704                         AddPriorityHeader (message);
 705
 706                         boundaryIndex = 0;
 707                         if (message.Attachments.Count > 0)
 708                                 SendWithAttachments (message);
 709                         else
 710                                 SendWithoutAttachments (message, null, false);
 711
 712                         SendDot ();
 713
 714                         status = Read ();
 715                         if (IsError (status))
 716                                 throw new SmtpException (status.StatusCode, status.Description);
 717
 718                         try {
 719                                 status = SendCommand ("QUIT");
 720                         } catch (System.IO.IOException) {
 721                                 // We excuse server for the rude connection closing as a response to QUIT
 722                         }
 723                 }
 724
 725                 public void Send (string from, string to, string subject, string body)
 726                 {
 727                         Send (new MailMessage (from, to, subject, body));
 728                 }
 729
 730 #if NET_4_5
 731                 public Task SendMailAsync (MailMessage message)
 732                 {
 733                         var tcs = new TaskCompletionSource<object> ();
 734                         SendCompletedEventHandler handler = null;
 735                         handler = (s, e) => SendMailAsyncCompletedHandler (tcs, e, handler, this);
 736                         SendCompleted += handler;
 737                         SendAsync (message, tcs);
 738                         return tcs.Task;
 739                 }
 740
 741                 public Task SendMailAsync (string from, string recipients, string subject, string body)
 742                 {
 743                         return SendMailAsync (new MailMessage (from, recipients, subject, body));
 744                 }
 745
 746                 static void SendMailAsyncCompletedHandler (TaskCompletionSource<object> source, AsyncCompletedEventArgs e, SendCompletedEventHandler handler, SmtpClient client)
 747                 {
 748                         if ((object) handler != e.UserState)
 749                                 return;
 750
 751                         client.SendCompleted -= handler;
 752
 753                         if (e.Error != null) {
 754                                 source.SetException (e.Error);
 755                                 return;
 756                         }
 757
 758                         if (e.Cancelled) {
 759                                 source.SetCanceled ();
 760                                 return;
 761                         }
 762
 763                         source.SetResult (null);
 764                 }
 765 #endif
 766
 767                 private void SendDot()
 768                 {
 769                         writer.Write(".\r\n");
 770                         writer.Flush();
 771                 }
 772
 773                 private void SendData (string data)
 774                 {
 775                         if (String.IsNullOrEmpty (data)) {
 776                                 writer.Write("\r\n");
 777                                 writer.Flush();
 778                                 return;
 779                         }
 780
 781                         StringReader sr = new StringReader (data);
 782                         string line;
 783                         bool escapeDots = deliveryMethod == SmtpDeliveryMethod.Network;
 784                         while ((line = sr.ReadLine ()) != null) {
 785                                 CheckCancellation ();
 786
 787                                 if (escapeDots) {
 788                                         int i;
 789                                         for (i = 0; i < line.Length; i++) {
 790                                                 if (line[i] != '.')
 791                                                         break;
 792                                         }
 793                                         if (i > 0 && i == line.Length) {
 794                                                 line += ".";
 795                                         }
 796                                 }
 797                                 writer.Write (line);
 798                                 writer.Write ("\r\n");
 799                         }
 800                         writer.Flush ();
 801                 }
 802
 803                 public void SendAsync (MailMessage message, object userToken)
 804                 {
 805                         if (worker != null)
 806                                 throw new InvalidOperationException ("Another SendAsync operation is in progress");
 807
 808                         worker = new BackgroundWorker ();
 809                         worker.DoWork += delegate (object o, DoWorkEventArgs ea) {
 810                                 try {
 811                                         user_async_state = ea.Argument;
 812                                         Send (message);
 813                                 } catch (Exception ex) {
 814                                         ea.Result = ex;
 815                                         throw ex;
 816                                 }
 817                         };
 818                         worker.WorkerSupportsCancellation = true;
 819                         worker.RunWorkerCompleted += delegate (object o, RunWorkerCompletedEventArgs ea) {
 820                                 // Note that RunWorkerCompletedEventArgs.UserState cannot be used (LAMESPEC)
 821                                 OnSendCompleted (new AsyncCompletedEventArgs (ea.Error, ea.Cancelled, user_async_state));
 822                         };
 823                         worker.RunWorkerAsync (userToken);
 824                 }
 825
 826                 public void SendAsync (string from, string to, string subject, string body, object userToken)
 827                 {
 828                         SendAsync (new MailMessage (from, to, subject, body), userToken);
 829                 }
 830
 831                 public void SendAsyncCancel ()
 832                 {
 833                         if (worker == null)
 834                                 throw new InvalidOperationException ("SendAsync operation is not in progress");
 835                         worker.CancelAsync ();
 836                 }
 837
 838                 private void AddPriorityHeader (MailMessage message) {
 839                         switch (message.Priority) {
 840                         case MailPriority.High:
 841                                 SendHeader (HeaderName.Priority, "Urgent");
 842                                 SendHeader (HeaderName.Importance, "high");
 843                                 SendHeader (HeaderName.XPriority, "1");
 844                                 break;
 845                         case MailPriority.Low:
 846                                 SendHeader (HeaderName.Priority, "Non-Urgent");
 847                                 SendHeader (HeaderName.Importance, "low");
 848                                 SendHeader (HeaderName.XPriority, "5");
 849                                 break;
 850                         }
 851                 }
 852
 853                 private void SendSimpleBody (MailMessage message) {
 854                         SendHeader (HeaderName.ContentType, message.BodyContentType.ToString ());
 855                         if (message.ContentTransferEncoding != TransferEncoding.SevenBit)
 856                                 SendHeader (HeaderName.ContentTransferEncoding, GetTransferEncodingName (message.ContentTransferEncoding));
 857                         SendData (string.Empty);
 858
 859                         SendData (EncodeBody (message));
 860                 }
 861
 862                 private void SendBodylessSingleAlternate (AlternateView av) {
 863                         SendHeader (HeaderName.ContentType, av.ContentType.ToString ());
 864                         if (av.TransferEncoding != TransferEncoding.SevenBit)
 865                                 SendHeader (HeaderName.ContentTransferEncoding, GetTransferEncodingName (av.TransferEncoding));
 866                         SendData (string.Empty);
 867
 868                         SendData (EncodeBody (av));
 869                 }
 870
 871                 private void SendWithoutAttachments (MailMessage message, string boundary, bool attachmentExists)
 872                 {
 873                         if (message.Body == null && message.AlternateViews.Count == 1)
 874                                 SendBodylessSingleAlternate (message.AlternateViews [0]);
 875                         else if (message.AlternateViews.Count > 0)
 876                                 SendBodyWithAlternateViews (message, boundary, attachmentExists);
 877                         else
 878                                 SendSimpleBody (message);
 879                 }
 880
 881
 882                 private void SendWithAttachments (MailMessage message) {
 883                         string boundary = GenerateBoundary ();
 884
 885                         // first "multipart/mixed"
 886                         ContentType messageContentType = new ContentType ();
 887                         messageContentType.Boundary = boundary;
 888                         messageContentType.MediaType = "multipart/mixed";
 889                         messageContentType.CharSet = null;
 890
 891                         SendHeader (HeaderName.ContentType, messageContentType.ToString ());
 892                         SendData (String.Empty);
 893
 894                         // body section
 895                         Attachment body = null;
 896
 897                         if (message.AlternateViews.Count > 0)
 898                                 SendWithoutAttachments (message, boundary, true);
 899                         else {
 900                                 body = Attachment.CreateAttachmentFromString (message.Body, null, message.BodyEncoding, message.IsBodyHtml ? "text/html" : "text/plain");
 901                                 message.Attachments.Insert (0, body);
 902                         }
 903
 904                         try {
 905                                 SendAttachments (message, body, boundary);
 906                         } finally {
 907                                 if (body != null)
 908                                         message.Attachments.Remove (body);
 909                         }
 910
 911                         EndSection (boundary);
 912                 }
 913
 914                 private void SendBodyWithAlternateViews (MailMessage message, string boundary, bool attachmentExists)
 915                 {
 916                         AlternateViewCollection alternateViews = message.AlternateViews;
 917
 918                         string inner_boundary = GenerateBoundary ();
 919
 920                         ContentType messageContentType = new ContentType ();
 921                         messageContentType.Boundary = inner_boundary;
 922                         messageContentType.MediaType = "multipart/alternative";
 923
 924                         if (!attachmentExists) {
 925                                 SendHeader (HeaderName.ContentType, messageContentType.ToString ());
 926                                 SendData (String.Empty);
 927                         }
 928
 929                         // body section
 930                         AlternateView body = null;
 931                         if (message.Body != null) {
 932                                 body = AlternateView.CreateAlternateViewFromString (message.Body, message.BodyEncoding, message.IsBodyHtml ? "text/html" : "text/plain");
 933                                 alternateViews.Insert (0, body);
 934                                 StartSection (boundary, messageContentType);
 935                         }
 936
 937 try {
 938                         // alternate view sections
 939                         foreach (AlternateView av in alternateViews) {
 940
 941                                 string alt_boundary = null;
 942                                 ContentType contentType;
 943                                 if (av.LinkedResources.Count > 0) {
 944                                         alt_boundary = GenerateBoundary ();
 945                                         contentType = new ContentType ("multipart/related");
 946                                         contentType.Boundary = alt_boundary;
 947
 948                                         contentType.Parameters ["type"] = av.ContentType.ToString ();
 949                                         StartSection (inner_boundary, contentType);
 950                                         StartSection (alt_boundary, av.ContentType, av);
 951                                 } else {
 952                                         contentType = new ContentType (av.ContentType.ToString ());
 953                                         StartSection (inner_boundary, contentType, av);
 954                                 }
 955
 956                                 switch (av.TransferEncoding) {
 957                                 case TransferEncoding.Base64:
 958                                         byte [] content = new byte [av.ContentStream.Length];
 959                                         av.ContentStream.Read (content, 0, content.Length);
 960                                             SendData (Convert.ToBase64String (content, Base64FormattingOptions.InsertLineBreaks));
 961                                         break;
 962                                 case TransferEncoding.QuotedPrintable:
 963                                         byte [] bytes = new byte [av.ContentStream.Length];
 964                                         av.ContentStream.Read (bytes, 0, bytes.Length);
 965                                         SendData (ToQuotedPrintable (bytes));
 966                                         break;
 967                                 case TransferEncoding.SevenBit:
 968                                 case TransferEncoding.Unknown:
 969                                         content = new byte [av.ContentStream.Length];
 970                                         av.ContentStream.Read (content, 0, content.Length);
 971                                         SendData (Encoding.ASCII.GetString (content));
 972                                         break;
 973                                 }
 974
 975                                 if (av.LinkedResources.Count > 0) {
 976                                         SendLinkedResources (message, av.LinkedResources, alt_boundary);
 977                                         EndSection (alt_boundary);
 978                                 }
 979
 980                                 if (!attachmentExists)
 981                                         SendData (string.Empty);
 982                         }
 983
 984 } finally {
 985                         if (body != null)
 986                                 alternateViews.Remove (body);
 987 }
 988                         EndSection (inner_boundary);
 989                 }
 990
 991                 private void SendLinkedResources (MailMessage message, LinkedResourceCollection resources, string boundary)
 992                 {
 993                         foreach (LinkedResource lr in resources) {
 994                                 StartSection (boundary, lr.ContentType, lr);
 995
 996                                 switch (lr.TransferEncoding) {
 997                                 case TransferEncoding.Base64:
 998                                         byte [] content = new byte [lr.ContentStream.Length];
 999                                         lr.ContentStream.Read (content, 0, content.Length);
1000                                             SendData (Convert.ToBase64String (content, Base64FormattingOptions.InsertLineBreaks));
1001                                         break;
1002                                 case TransferEncoding.QuotedPrintable:
1003                                         byte [] bytes = new byte [lr.ContentStream.Length];
1004                                         lr.ContentStream.Read (bytes, 0, bytes.Length);
1005                                         SendData (ToQuotedPrintable (bytes));
1006                                         break;
1007                                 case TransferEncoding.SevenBit:
1008                                 case TransferEncoding.Unknown:
1009                                         content = new byte [lr.ContentStream.Length];
1010                                         lr.ContentStream.Read (content, 0, content.Length);
1011                                         SendData (Encoding.ASCII.GetString (content));
1012                                         break;
1013                                 }
1014                         }
1015                 }
1016
1017                 private void SendAttachments (MailMessage message, Attachment body, string boundary) {
1018                         foreach (Attachment att in message.Attachments) {
1019                                 ContentType contentType = new ContentType (att.ContentType.ToString ());
1020                                 if (att.Name != null) {
1021                                         contentType.Name = att.Name;
1022                                         if (att.NameEncoding != null)
1023                                                 contentType.CharSet = att.NameEncoding.HeaderName;
1024                                         att.ContentDisposition.FileName = att.Name;
1025                                 }
1026                                 StartSection (boundary, contentType, att, att != body);
1027
1028                                 byte [] content = new byte [att.ContentStream.Length];
1029                                 att.ContentStream.Read (content, 0, content.Length);
1030                                 switch (att.TransferEncoding) {
1031                                 case TransferEncoding.Base64:
1032                                         SendData (Convert.ToBase64String (content, Base64FormattingOptions.InsertLineBreaks));
1033                                         break;
1034                                 case TransferEncoding.QuotedPrintable:
1035                                         SendData (ToQuotedPrintable (content));
1036                                         break;
1037                                 case TransferEncoding.SevenBit:
1038                                 case TransferEncoding.Unknown:
1039                                         SendData (Encoding.ASCII.GetString (content));
1040                                         break;
1041                                 }
1042
1043                                 SendData (string.Empty);
1044                         }
1045                 }
1046
1047                 private SmtpResponse SendCommand (string command)
1048                 {
1049                         writer.Write (command);
1050                         // Certain SMTP servers will reject mail sent with unix line-endings; see http://cr.yp.to/docs/smtplf.html
1051                         writer.Write ("\r\n");
1052                         writer.Flush ();
1053                         return Read ();
1054                 }
1055
1056                 private void SendHeader (string name, string value)
1057                 {
1058                         SendData (String.Format ("{0}: {1}", name, value));
1059                 }
1060
1061                 private void StartSection (string section, ContentType sectionContentType)
1062                 {
1063                         SendData (String.Format ("--{0}", section));
1064                         SendHeader ("content-type", sectionContentType.ToString ());
1065                         SendData (string.Empty);
1066                 }
1067
1068                 private void StartSection (string section, ContentType sectionContentType, AttachmentBase att)
1069                 {
1070                         SendData (String.Format ("--{0}", section));
1071                         SendHeader ("content-type", sectionContentType.ToString ());
1072                         SendHeader ("content-transfer-encoding", GetTransferEncodingName (att.TransferEncoding));
1073                         if (!string.IsNullOrEmpty (att.ContentId))
1074                                 SendHeader("content-ID", "<" + att.ContentId + ">");
1075                         SendData (string.Empty);
1076                 }
1077
1078                 private void StartSection (string section, ContentType sectionContentType, Attachment att, bool sendDisposition) {
1079                         SendData (String.Format ("--{0}", section));
1080                         if (!string.IsNullOrEmpty (att.ContentId))
1081                                 SendHeader("content-ID", "<" + att.ContentId + ">");
1082                         SendHeader ("content-type", sectionContentType.ToString ());
1083                         SendHeader ("content-transfer-encoding", GetTransferEncodingName (att.TransferEncoding));
1084                         if (sendDisposition)
1085                                 SendHeader ("content-disposition", att.ContentDisposition.ToString ());
1086                         SendData (string.Empty);
1087                 }
1088
1089                 // use proper encoding to escape input
1090                 private string ToQuotedPrintable (string input, Encoding enc)
1091                 {
1092                         byte [] bytes = enc.GetBytes (input);
1093                         return ToQuotedPrintable (bytes);
1094                 }
1095
1096                 private string ToQuotedPrintable (byte [] bytes)
1097                 {
1098                         StringWriter writer = new StringWriter ();
1099                         int charsInLine = 0;
1100                         int curLen;
1101                         StringBuilder sb = new StringBuilder("=", 3);
1102                         byte equalSign = (byte)'=';
1103                         char c = (char)0;
1104
1105                         foreach (byte i in bytes) {
1106                                 if (i > 127 || i == equalSign) {
1107                                         sb.Length = 1;
1108                                         sb.Append(Convert.ToString (i, 16).ToUpperInvariant ());
1109                                         curLen = 3;
1110                                 } else {
1111                                         c = Convert.ToChar (i);
1112                                         if (c == '\r' || c == '\n') {
1113                                                 writer.Write (c);
1114                                                 charsInLine = 0;
1115                                                 continue;
1116                                         }
1117                                         curLen = 1;
1118                                 }
1119
1120                                 charsInLine += curLen;
1121                                 if (charsInLine > 75) {
1122                                         writer.Write ("=\r\n");
1123                                         charsInLine = curLen;
1124                                 }
1125                                 if (curLen == 1)
1126                                         writer.Write (c);
1127                                 else
1128                                         writer.Write (sb.ToString ());
1129                         }
1130
1131                         return writer.ToString ();
1132                 }
1133                 private static string GetTransferEncodingName (TransferEncoding encoding)
1134                 {
1135                         switch (encoding) {
1136                         case TransferEncoding.QuotedPrintable:
1137                                 return "quoted-printable";
1138                         case TransferEncoding.SevenBit:
1139                                 return "7bit";
1140                         case TransferEncoding.Base64:
1141                                 return "base64";
1142                         }
1143                         return "unknown";
1144                 }
1145
1146 #if SECURITY_DEP
1147                 RemoteCertificateValidationCallback callback = delegate (object sender,
1148                                                                          X509Certificate certificate,
1149                                                                          X509Chain chain,
1150                                                                          SslPolicyErrors sslPolicyErrors) {
1151                         // honor any exciting callback defined on ServicePointManager
1152                         if (ServicePointManager.ServerCertificateValidationCallback != null)
1153                                 return ServicePointManager.ServerCertificateValidationCallback (sender, certificate, chain, sslPolicyErrors);
1154                         // otherwise provide our own
1155                         if (sslPolicyErrors != SslPolicyErrors.None)
1156                                 throw new InvalidOperationException ("SSL authentication error: " + sslPolicyErrors);
1157                         return true;
1158                         };
1159 #endif
1160
1161                 private void InitiateSecureConnection () {
1162                         SmtpResponse response = SendCommand ("STARTTLS");
1163
1164                         if (IsError (response)) {
1165                                 throw new SmtpException (SmtpStatusCode.GeneralFailure, "Server does not support secure connections.");
1166                         }
1167
1168 #if   SECURITY_DEP
1169                         SslStream sslStream = new SslStream (stream, false, callback, null);
1170                         CheckCancellation ();
1171                         sslStream.AuthenticateAsClient (Host, this.ClientCertificates, SslProtocols.Default, false);
1172                         stream = sslStream;
1173
1174 #else
1175                         throw new SystemException ("You are using an incomplete System.dll build");
1176 #endif
1177                 }
1178
1179                 void Authenticate ()
1180                 {
1181                         string user = null, pass = null;
1182
1183                         if (UseDefaultCredentials) {
1184                                 user = CredentialCache.DefaultCredentials.GetCredential (new System.Uri ("smtp://" + host), "basic").UserName;
1185                                 pass =  CredentialCache.DefaultCredentials.GetCredential (new System.Uri ("smtp://" + host), "basic").Password;
1186                         } else if (Credentials != null) {
1187                                 user = Credentials.GetCredential (host, port, "smtp").UserName;
1188                                 pass = Credentials.GetCredential (host, port, "smtp").Password;
1189                         } else {
1190                                 return;
1191                         }
1192
1193                         Authenticate (user, pass);
1194                 }
1195
1196                 void CheckStatus (SmtpResponse status, int i)
1197                 {
1198                         if (((int) status.StatusCode) != i)
1199                                 throw new SmtpException (status.StatusCode, status.Description);
1200                 }
1201
1202                 void ThrowIfError (SmtpResponse status)
1203                 {
1204                         if (IsError (status))
1205                                 throw new SmtpException (status.StatusCode, status.Description);
1206                 }
1207
1208                 void Authenticate (string user, string password)
1209                 {
1210                         if (authMechs == AuthMechs.None)
1211                                 return;
1212
1213                         SmtpResponse status;
1214                         /*
1215                         if ((authMechs & AuthMechs.DigestMD5) != 0) {
1216                                 status = SendCommand ("AUTH DIGEST-MD5");
1217                                 CheckStatus (status, 334);
1218                                 string challenge = Encoding.ASCII.GetString (Convert.FromBase64String (status.Description.Substring (4)));
1219                                 Console.WriteLine ("CHALLENGE: {0}", challenge);
1220                                 DigestSession session = new DigestSession ();
1221                                 session.Parse (false, challenge);
1222                                 string response = session.Authenticate (this, user, password);
1223                                 status = SendCommand (Convert.ToBase64String (Encoding.UTF8.GetBytes (response)));
1224                                 CheckStatus (status, 235);
1225                         } else */
1226                         if ((authMechs & AuthMechs.Login) != 0) {
1227                                 status = SendCommand ("AUTH LOGIN");
1228                                 CheckStatus (status, 334);
1229                                 status = SendCommand (Convert.ToBase64String (Encoding.UTF8.GetBytes (user)));
1230                                 CheckStatus (status, 334);
1231                                 status = SendCommand (Convert.ToBase64String (Encoding.UTF8.GetBytes (password)));
1232                                 CheckStatus (status, 235);
1233                         } else if ((authMechs & AuthMechs.Plain) != 0) {
1234                                 string s = String.Format ("\0{0}\0{1}", user, password);
1235                                 s = Convert.ToBase64String (Encoding.UTF8.GetBytes (s));
1236                                 status = SendCommand ("AUTH PLAIN " + s);
1237                                 CheckStatus (status, 235);
1238                         } else {
1239                                 throw new SmtpException ("AUTH types PLAIN, LOGIN not supported by the server");
1240                         }
1241                 }
1242
1243                 #endregion // Methods
1244
1245                 // The HeaderName struct is used to store constant string values representing mail headers.
1246                 private struct HeaderName {
1247                         public const string ContentTransferEncoding = "Content-Transfer-Encoding";
1248                         public const string ContentType = "Content-Type";
1249                         public const string Bcc = "Bcc";
1250                         public const string Cc = "Cc";
1251                         public const string From = "From";
1252                         public const string Subject = "Subject";
1253                         public const string To = "To";
1254                         public const string MimeVersion = "MIME-Version";
1255                         public const string MessageId = "Message-ID";
1256                         public const string Priority = "Priority";
1257                         public const string Importance = "Importance";
1258                         public const string XPriority = "X-Priority";
1259                         public const string Date = "Date";
1260                 }
1261
1262                 // This object encapsulates the status code and description of an SMTP response.
1263                 private struct SmtpResponse {
1264                         public SmtpStatusCode StatusCode;
1265                         public string Description;
1266
1267                         public static SmtpResponse Parse (string line) {
1268                                 SmtpResponse response = new SmtpResponse ();
1269
1270                                 if (line.Length < 4)
1271                                         throw new SmtpException ("Response is to short " +
1272                                                                  line.Length + ".");
1273
1274                                 if ((line [3] != ' ') && (line [3] != '-'))
1275                                         throw new SmtpException ("Response format is wrong.(" +
1276                                                                  line + ")");
1277
1278                                 // parse the response code
1279                                 response.StatusCode = (SmtpStatusCode) Int32.Parse (line.Substring (0, 3));
1280
1281                                 // set the raw response
1282                                 response.Description = line;
1283
1284                                 return response;
1285                         }
1286                 }
1287         }
1288
1289         class CCredentialsByHost : ICredentialsByHost
1290         {
1291                 public CCredentialsByHost (string userName, string password) {
1292                         this.userName = userName;
1293                         this.password = password;
1294                 }
1295
1296                 public NetworkCredential GetCredential (string host, int port, string authenticationType) {
1297                         return new NetworkCredential (userName, password);
1298                 }
1299
1300                 private string userName;
1301                 private string password;
1302         }
1303 }
1304