src/org/ibex/mail/SMTP.java

   1 // Copyright 2000-2005 the Contributors, as shown in the revision logs.
   2 // Licensed under the Apache Public Source License 2.0 ("the License").
   3 // You may not use this file except in compliance with the License.
   4
   5 package org.ibex.mail;
   6 import org.ibex.mail.target.*;
   7 import org.ibex.util.*;
   8 import org.ibex.net.*;
   9 import org.ibex.io.*;
  10 import java.net.*;
  11 import java.io.*;
  12 import java.util.*;
  13 import java.text.*;
  14 import javax.naming.*;
  15 import javax.naming.directory.*;
  16
  17 // FIXME: inbound throttling/ratelimiting
  18
  19 // "Address enumeration detection" -- notice when it looks like somebody
  20 // is trying a raft of addresses.
  21
  22 // RFC's implemented
  23 // RFC2554: SMTP Service Extension for Authentication
  24 //     - did not implement section 5, though
  25 // RFC4616: SASL PLAIN
  26
  27 // Note: we can't actually use status codes for feedback if we accept
  28 // multiple destination addresses...  a failure on one and success on
  29 // the other...
  30
  31 // FIXME: logging: current logging sucks
  32 // FIXME: loop prevention
  33 // FIXME: probably need some throttling on outbound mail
  34
  35 // FEATURE: public static boolean validate(Address a)
  36 // FEATURE: rate-limiting
  37
  38 // FEATURE: infer messageid, date, if not present (?)
  39 // FEATURE: exponential backoff on retry time?
  40 // FEATURE: RFC2822, section 4.5.1: special "postmaster" address
  41 // FEATURE: RFC2822, section 4.5.4.1: retry strategies
  42 // FEATURE: RFC2822, section 5, multiple MX records, preferences, ordering
  43 // FEATURE: RFC2822, end of 4.1.2: backslashes in headers
  44 public class SMTP {
  45
  46     public static final SimpleDateFormat dateFormat = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z");
  47     public static final int numOutgoingThreads = 5;
  48
  49     private static final SqliteMailbox allmail =
  50         (SqliteMailbox)FileBasedMailbox
  51         .getFileBasedMailbox("/afs/megacz.com/mail/user/megacz/allmail", false);
  52
  53     public static final int GRAYLIST_MINWAIT =  1000 * 60 * 60;           // one hour
  54     public static final int GRAYLIST_MAXWAIT =  1000 * 60 * 60 * 24 * 5;  // five days
  55
  56     public static final int RETRY_TIME = 1000 * 60 * 30;
  57
  58     public static final Graylist graylist;
  59     public static final Whitelist whitelist;
  60     static {
  61         try {
  62             graylist =  new Graylist(Mailbox.STORAGE_ROOT+"/db/graylist.sqlite");
  63             whitelist = new Whitelist(Mailbox.STORAGE_ROOT+"/db/whitelist.sqlite");
  64         } catch (Exception e) {
  65             throw new RuntimeException(e);
  66         }
  67     }
  68
  69     public static final int MAX_MESSAGE_SIZE =
  70         Integer.parseInt(System.getProperty("org.ibex.mail.smtp.maxMessageSize", "-1"));
  71
  72     private static final Mailbox spool =
  73         FileBasedMailbox.getFileBasedMailbox(Mailbox.STORAGE_ROOT,false).slash("spool",true).slash("smtp",true).getMailbox();
  74
  75     static {
  76         for(int i=0; i<numOutgoingThreads; i++)
  77             new Outgoing().start();
  78     }
  79
  80     public static void enqueue(Message m) throws IOException {
  81         if (!m.envelopeTo.isLocal()) Outgoing.enqueue(m);
  82         else {
  83             try {
  84                 allmail.accept(m);
  85             } catch (Exception e) {
  86                 // FIXME incredibly gross hack
  87                 if (e.toString().indexOf("attempt to insert two messages with identical messageid")==-1)
  88                     Log.error(SMTP.class, e);
  89             }
  90             Target.root.accept(m);
  91         }
  92     }
  93
  94     public static class SMTPException extends MailException {
  95         int code;
  96         String message;
  97         public SMTPException(String s) {
  98             try {
  99                 code = Integer.parseInt(s.substring(0, s.indexOf(' ')));
 100                 message = s.substring(s.indexOf(' ')+1);
 101             } catch (NumberFormatException nfe) {
 102                 code = -1;
 103                 message = s;
 104             }
 105         }
 106         public String toString() { return "SMTP " + code + ": " + message; }
 107         public String getMessage() { return toString(); }
 108     }
 109
 110     // Server //////////////////////////////////////////////////////////////////////////////
 111
 112     public static class Server {
 113         public void handleRequest(Connection conn) throws IOException {
 114             conn.setTimeout(5 * 60 * 1000);
 115             conn.setNewline("\r\n");
 116             conn.println("220 " + conn.vhost + " ESMTP " + this.getClass().getName());
 117             Address from = null;
 118             Vector to = new Vector();
 119             boolean ehlo = false;
 120             String remotehost = null;
 121             String authenticatedAs = null;
 122             int failedRcptCount = 0;
 123             for(String command = conn.readln(); ; command = conn.readln()) try {
 124                 if (command == null) return;
 125                 Log.warn("**"+conn.getRemoteAddress()+"**", command);
 126                 String c = command.toUpperCase();
 127                 if (c.startsWith("HELO"))        {
 128                     remotehost = c.substring(5).trim();
 129                     conn.println("250 HELO " + conn.vhost);
 130                     from = null; to = new Vector();
 131                 } else if (c.startsWith("EHLO")) {
 132                     remotehost = c.substring(5).trim();
 133                     conn.println("250-"+conn.vhost);
 134                     //conn.println("250-AUTH");
 135                     conn.println("250-AUTH PLAIN");
 136                     //conn.println("250-STARTTLS");
 137                     conn.println("250 HELP");
 138                     ehlo = true;
 139                     from = null; to = new Vector();
 140                 } else if (c.startsWith("RSET")) { conn.println("250 reset ok");           from = null; to = new Vector();
 141                 } else if (c.startsWith("HELP")) { conn.println("214 you are beyond help.  see a trained professional.");
 142                 } else if (c.startsWith("VRFY")) { conn.println("502 VRFY not supported");
 143                 } else if (c.startsWith("EXPN")) { conn.println("502 EXPN not supported");
 144                 } else if (c.startsWith("NOOP")) { conn.println("250 OK");
 145                 } else if (c.startsWith("QUIT")) { conn.println("221 " + conn.vhost + " closing connection"); return;
 146                 } else if (c.startsWith("STARTTLS")) {
 147                     conn.println("220 starting TLS...");
 148                     conn.flush();
 149                     conn = conn.negotiateSSL(true);
 150                     from = null; to = new Vector();
 151                 } else if (c.startsWith("AUTH")) {
 152                     if (authenticatedAs != null) {
 153                         conn.println("503 you are already authenticated; you must reconnect to reauth");
 154                     } else {
 155                         String mechanism = command.substring(4).trim();
 156                         String rest = "";
 157                         if (mechanism.indexOf(' ')!=-1) {
 158                             rest      = mechanism.substring(mechanism.indexOf(' ')+1).trim();
 159                             mechanism = mechanism.substring(0, mechanism.indexOf(' '));
 160                         }
 161                         if (mechanism.equals("PLAIN")) {
 162                             // 538 Encryption required for requested authentication mechanism?
 163                             byte[] bytes = Encode.fromBase64(rest);
 164                             String authenticateUser = null;
 165                             String authorizeUser = null;
 166                             String password = null;
 167                             int start = 0;
 168                             for(int i=0; i<=bytes.length; i++) {
 169                                 if (i<bytes.length && bytes[i]!=0) continue;
 170                                 String result = new String(bytes, start, i-start, "UTF-8");
 171                                 if (authenticateUser==null)   authenticateUser = result;
 172                                 else if (authorizeUser==null) authorizeUser = result;
 173                                 else if (password==null)      password = result;
 174                                 start = i+1;
 175                             }
 176                             // FIXME: be smarter here
 177                             if (Main.auth.login(authorizeUser, password)!=null)
 178                                 authenticatedAs = authenticateUser;
 179                             conn.println("235 Authentication successful");
 180                             /*
 181                         } else if (mechanism.equals("CRAM-MD5")) {
 182                             String challenge = ;
 183                             conn.println("334 "+challenge);
 184                             String resp = conn.readln();
 185                             if (resp.equals("*")) {
 186                                 conn.println("501 client requested AUTH cancellation");
 187                             }
 188                         } else if (mechanism.equals("ANONYMOUS")) {
 189                         } else if (mechanism.equals("EXTERNAL")) {
 190                         } else if (mechanism.equals("DIGEST-MD5")) {
 191                             */
 192                         } else {
 193                             conn.println("504 unrecognized authentication type");
 194                         }
 195                         // on success, reset to initial state; client will EHLO again
 196                         from = null; to = new Vector();
 197                     }
 198                 } else if (c.startsWith("MAIL FROM:")) {
 199                     command = command.substring(10).trim();
 200                     from = command.equals("<>") ? null : new Address(command);
 201                     conn.println("250 " + from + " is syntactically correct");
 202                     // Don't perform SAV; discouraged here
 203                     //   http://blog.fastmail.fm/2007/12/05/sending-email-servers-best-practice/
 204                 } else if (c.startsWith("RCPT TO:")) {
 205                     // some clients are broken and put RCPT first; we will tolerate this
 206                     command = command.substring(8).trim();
 207                     if(command.indexOf(' ') != -1) command = command.substring(0, command.indexOf(' '));
 208                     Address addr = new Address(command);
 209                     if (conn.getRemoteAddress().isLoopbackAddress() || (from!=null&&from.toString().indexOf("johnw")!=-1)) {
 210                         conn.println("250 you are connected locally, so I will let you send");
 211                         to.addElement(addr);
 212                         if (!whitelist.isWhitelisted(addr))
 213                             whitelist.addWhitelist(addr);
 214                     } else if (authenticatedAs!=null) {
 215                         conn.println("250 you are authenticated as "+authenticatedAs+", so I will let you send");
 216                         to.addElement(addr);
 217                         if (!whitelist.isWhitelisted(addr))
 218                             whitelist.addWhitelist(addr);
 219                     } else if (addr.isLocal()) {
 220                         if (to.size() > 3) {
 221                             conn.println("536 sorry, limit on 3 RCPT TO's per DATA");
 222                         } else {
 223                             // FEATURE: should check the address further and give 550 if undeliverable
 224                             conn.println("250 " + addr + " is on this machine; I will deliver it");
 225                             to.addElement(addr);
 226                         }
 227                     } else {
 228                         conn.println("535 sorry, " + addr + " is not on this machine, you are not connected from localhost, and I will not relay without SMTP AUTH");
 229                         Log.warn("","535 sorry, " + addr + " is not on this machine, you are not connected from localhost, and I will not relay without SMTP AUTH");
 230                         failedRcptCount++;
 231                         if (failedRcptCount > 3) {
 232                             conn.close();
 233                             return;
 234                         }
 235                     }
 236                     conn.flush();
 237                 } else if (c.startsWith("DATA")) {
 238                     //if (from == null) { conn.println("503 MAIL FROM command must precede DATA"); continue; }
 239                     if (to == null || to.size()==0) { conn.println("503 RCPT TO command must precede DATA"); continue; }
 240                     if (!graylist.isWhitelisted(conn.getRemoteAddress()) && !conn.getRemoteAddress().isLoopbackAddress() && authenticatedAs==null) {
 241                         long when = graylist.getGrayListTimestamp(conn.getRemoteAddress(), from+"", to+"");
 242                         if (when == 0 || System.currentTimeMillis() - when > GRAYLIST_MAXWAIT) {
 243                             graylist.setGrayListTimestamp(conn.getRemoteAddress(), from+"", to+"",  System.currentTimeMillis());
 244                             conn.println("451 you are graylisted; please try back in one hour to be whitelisted");
 245                             Log.warn(conn.getRemoteAddress().toString(), "451 you are graylisted; please try back in one hour to be whitelisted");
 246                             conn.flush();
 247                             continue;
 248                         } else if (System.currentTimeMillis() - when > GRAYLIST_MINWAIT) {
 249                             graylist.addWhitelist(conn.getRemoteAddress());
 250                             conn.println("354 (you have been whitelisted) Enter message, ending with \".\" on a line by itself");
 251                             Log.warn(conn.getRemoteAddress().toString(), "has been whitelisted");
 252                         } else {
 253                             conn.println("451 you are still graylisted (since "+new java.util.Date(when)+")");
 254                             conn.flush();
 255                             Log.warn(conn.getRemoteAddress().toString(), "451 you are still graylisted (since "+new java.util.Date(when)+")");
 256                             continue;
 257                         }
 258                     } else {
 259                         conn.println("354 Enter message, ending with \".\" on a line by itself");
 260                     }
 261                     conn.flush();
 262                     try {
 263                         // FIXME: deal with messages larger than memory here?
 264                         StringBuffer buf = new StringBuffer();
 265                         buf.append("Received: from " + conn.getRemoteHostname() + " (" + remotehost + ")\r\n");
 266                         buf.append("          by "+conn.vhost+" ("+SMTP.class.getName()+") with "+(ehlo?"ESMTP":"SMTP") + "\r\n");
 267                         buf.append("          for ");
 268                         // FIXME: this is leaking BCC addrs
 269                         // for(int i=0; i<to.size(); i++) buf.append(to.elementAt(i) + " ");
 270                         buf.append("; " + dateFormat.format(new Date()) + "\r\n");
 271
 272                         // FIXME: some sort of stream transformer here?
 273                         while(true) {
 274                             String s = conn.readln();
 275                             if (s == null) throw new RuntimeException("connection closed");
 276                             if (s.equals(".")) break;
 277                             if (s.startsWith(".")) s = s.substring(1);
 278                             buf.append(s + "\r\n");
 279                             if (MAX_MESSAGE_SIZE != -1 && buf.length() > MAX_MESSAGE_SIZE && (from+"").indexOf("paperless")==-1) {
 280                                 Log.error("**"+conn.getRemoteAddress()+"**",
 281                                           "sorry, this mail server only accepts messages of less than " +
 282                                           ByteSize.toString(MAX_MESSAGE_SIZE));
 283                                 throw new MailException.Malformed("sorry, this mail server only accepts messages of less than " +
 284                                                                   ByteSize.toString(MAX_MESSAGE_SIZE));
 285                             }
 286                         }
 287                         String message = buf.toString();
 288                         Message m = null;
 289                         for(int i=0; i<to.size(); i++)
 290                             enqueue(m = Message.newMessage(Fountain.Util.create(message)).withEnvelope(from, (Address)to.elementAt(i)));
 291                         if (m != null) Log.info(SMTP.class, "accepted message: " + m.summary());
 292                         conn.println("250 message accepted");
 293                         conn.flush();
 294                         from = null; to = new Vector();
 295                     } catch (MailException.Malformed mfe) {    conn.println("501 " + mfe.toString());
 296                     } catch (MailException.MailboxFull mbf) {  conn.println("452 " + mbf);
 297                     } catch (Script.Later.LaterException le) { conn.println("453 try again later");
 298                     } catch (Script.Reject.RejectException re) {
 299                         Log.warn(SMTP.class, "rejecting message due to: " + re.reason + "\n   " + re.m.summary());
 300                         conn.println("501 " + re.reason);
 301                     }
 302                 } else                    { conn.println("500 unrecognized command"); }
 303             } catch (Message.Malformed e) { conn.println("501 " + e.toString()); }
 304         }
 305     }
 306
 307
 308     // Outgoing Mail Thread //////////////////////////////////////////////////////////////////////////////
 309
 310     public static class Outgoing extends Thread {
 311
 312         private static final HashMap deadHosts = new HashMap();
 313         public static void enqueue(Message m) throws IOException {
 314             if (m == null) { Log.warn(Outgoing.class, "attempted to enqueue(null)"); return; }
 315             String traces = m.headers.get("Received");
 316             if (traces!=null) {
 317                 int lines = 0;
 318                 for(int i=0; i<traces.length(); i++)
 319                     if (traces.charAt(i)=='\n' || traces.charAt(i)=='\r')
 320                         lines++;
 321                 if (lines > 100) { // required by rfc
 322                     Log.warn(SMTP.Outgoing.class, "Message with " + lines + " trace hops; dropping\n" + m.summary());
 323                     return;
 324                 }
 325             }
 326             synchronized(Outgoing.class) {
 327                 spool.insert(m, Mailbox.Flag.defaultFlags);
 328                 Outgoing.class.notifyAll();
 329             }
 330         }
 331
 332         public static boolean attempt(Message m) throws IOException { return attempt(m, false); }
 333         public static boolean attempt(Message m, boolean noBounces) throws IOException {
 334             if (m.envelopeTo == null) {
 335                 Log.warn(SMTP.Outgoing.class, "aieeee, null envelopeTo: " + m.summary());
 336                 return false;
 337             }
 338             InetAddress[] mx = getMailExchangerIPs(m.envelopeTo.host);
 339             if (mx.length == 0) {
 340                 if (!noBounces) {
 341                     enqueue(m.bounce("could not resolve " + m.envelopeTo.host));
 342                     return true;
 343                 } else {
 344                     Log.warn(SMTP.Outgoing.class, "could not resolve " + m.envelopeTo.host);
 345                     return false;
 346                 }
 347             }
 348             if (new Date().getTime() - m.arrival.getTime() > 1000 * 60 * 60 * 24 * 5) {
 349                 if (!noBounces) {
 350                     enqueue(m.bounce("could not send for 5 days"));
 351                     return true;
 352                 } else {
 353                     Log.warn(SMTP.Outgoing.class, "could not send for 5 days: " + m.summary());
 354                     return false;
 355                 }
 356             }
 357             for(int i=0; i<mx.length; i++) {
 358                 //if (deadHosts.contains(mx[i])) continue;
 359                 if (attempt(m, mx[i])) return true;
 360             }
 361             return false;
 362         }
 363
 364         private static void check(String s, Connection conn) {
 365             if (s==null) return;
 366             while (s.length() > 3 && s.charAt(3) == '-') s = conn.readln();
 367             //if (s.startsWith("4")||s.startsWith("5")) throw new SMTPException(s);
 368             if (!s.startsWith("2")&&!s.startsWith("3")) throw new SMTPException(s);
 369         }
 370         private static boolean attempt(final Message m, final InetAddress mx) {
 371             boolean accepted = false;
 372             Connection conn = null;
 373             try {
 374                 conn = new Connection(new Socket(mx, 25), InetAddress.getLocalHost().getHostName());
 375                 InetAddress localAddress = conn.getSocket().getLocalAddress();
 376                 String reverse = DNSUtil.reverseLookup(localAddress);
 377                 Log.info(SMTP.Outgoing.class,
 378                          "outbound connection to " + mx + " uses " + localAddress + " [reverse: " + reverse + "]");
 379                 InetAddress relookup = InetAddress.getByName(reverse);
 380                 if (!relookup.equals(localAddress))
 381                     Log.error(SMTP.Outgoing.class,
 382                               "Warning: local machine fails forward-confirmed-reverse; " +
 383                               reverse + " resolves to " + localAddress);
 384                 conn.setNewline("\r\n");
 385                 conn.setTimeout(60 * 1000);
 386                 check(conn.readln(), conn);  // banner
 387                 try {
 388                     conn.println("EHLO " + reverse);
 389                     check(conn.readln(), conn);
 390                 } catch (SMTPException smtpe) {
 391                     conn.println("HELO " + reverse);
 392                     check(conn.readln(), conn);
 393                 }
 394                 String envelopeFrom = m.envelopeFrom==null ? "" : m.envelopeFrom.toString();
 395                 conn.println("MAIL FROM:<" + envelopeFrom +">");            check(conn.readln(), conn);
 396                 conn.println("RCPT TO:<"   + m.envelopeTo.toString()+">");  check(conn.readln(), conn);
 397                 conn.println("DATA");                                       check(conn.readln(), conn);
 398
 399                 Headers head = new Headers(m.headers,
 400                                            new String[] {
 401                                                "return-path", null,
 402                                                "bcc", null
 403                                            });
 404                 Stream stream = head.getStream();
 405                 for(String s = stream.readln(); s!=null; s=stream.readln()) {
 406                     if (s.startsWith(".")) conn.print(".");
 407                     conn.println(s);
 408                 }
 409                 conn.println("");
 410                 stream = m.getBody().getStream();
 411                 for(String s = stream.readln(); s!=null; s=stream.readln()) {
 412                     if (s.startsWith(".")) conn.print(".");
 413                     conn.println(s);
 414                 }
 415                 conn.println(".");
 416                 String resp = conn.readln();
 417                 if (resp == null)
 418                     throw new SMTPException("server " + mx + " closed connection without accepting message");
 419                 check(resp, conn);
 420                 Log.warn(SMTP.Outgoing.class, "success: " + mx + " accepted " + m.summary() + "\n["+resp+"]");
 421                 accepted = true;
 422                 conn.close();
 423             } catch (SMTPException e) {
 424                 if (accepted) return true;
 425                 Log.warn(SMTP.Outgoing.class, "    unable to send; error=" + e);
 426                 Log.warn(SMTP.Outgoing.class, "      message: " + m.summary());
 427                 Log.warn(SMTP.Outgoing.class, e);
 428                 /*
 429                   // FIXME: we should not be bouncing here!
 430                 if (e.code >= 500 && e.code <= 599) {
 431                     try {
 432                         attempt(m.bounce("unable to deliver: " + e), true);
 433                     } catch (Exception ex) {
 434                         Log.error(SMTP.Outgoing.class, "exception while trying to deliver bounce; giving up completely");
 435                         Log.error(SMTP.Outgoing.class, ex);
 436                     }
 437                     return true;
 438                 }
 439                 */
 440                 return false;
 441             } catch (Exception e) {
 442                 if (accepted) return true;
 443                 Log.warn(SMTP.Outgoing.class, "    unable to send; error=" + e);
 444                 Log.warn(SMTP.Outgoing.class, "      message: " + m.summary());
 445                 Log.warn(SMTP.Outgoing.class, e);
 446                 //if (conn != null) Log.warn(SMTP.Outgoing.class, conn.dumpLog());
 447                 return false;
 448             } finally {
 449                 if (conn != null) conn.close();
 450             }
 451             return accepted;
 452         }
 453
 454         private static HashSet<Outgoing> threads = new HashSet<Outgoing>();
 455         private static int serials = 1;
 456         private int serial = serials++;
 457         private Mailbox.Iterator it;
 458
 459         private static Map<String,Long> nextTry = Collections.synchronizedMap(new HashMap<String,Long>());
 460
 461         public Outgoing() {
 462             synchronized(Outgoing.class) {
 463                 threads.add(this);
 464             }
 465         }
 466
 467         public void wake() {
 468             int count = spool.count(Query.all());
 469             Log.info(SMTP.Outgoing.class, "outgoing thread #"+serial+" woke up; " + count + " messages to send");
 470             try {
 471                 while(true) {
 472                     boolean good = false;
 473                     synchronized(Outgoing.class) {
 474                         it = spool.iterator();
 475                         OUTER: for(; it.next(); ) {
 476                             for(Outgoing o : threads)
 477                                 if (o!=this && o.it != null && o.it.uid()==it.uid())
 478                                     continue OUTER;
 479                             good = true;
 480                             break;
 481                         }
 482                     }
 483                     if (!good) break;
 484                     try {
 485                         String messageid = it.cur().messageid;
 486                         if (nextTry.get(messageid) == null || System.currentTimeMillis() > nextTry.get(messageid)) {
 487                             boolean ok = attempt(it.cur());
 488                             if (ok) it.delete();
 489                             else nextTry.put(messageid, System.currentTimeMillis() + RETRY_TIME);
 490                         }
 491                     } catch (Exception e) {
 492                         Log.error(SMTP.Outgoing.class, e);
 493                     }
 494                     Log.info(this, "sleeping for 3s...");
 495                     Thread.sleep(3000);
 496                 }
 497             } catch (Exception e) {
 498                 //if (e instanceof InterruptedException) throw e;
 499                 Log.error(SMTP.Outgoing.class, e);
 500             }
 501             Log.info(SMTP.Outgoing.class, "outgoing thread #"+serial+" going back to sleep");
 502             it = null;
 503         }
 504
 505         public void run() {
 506             try {
 507                 while(true) {
 508                     Log.setThreadAnnotation("[outgoing #"+serial+"] ");
 509                     wake();
 510                     Thread.sleep(1000);
 511                     synchronized(Outgoing.class) {
 512                         Outgoing.class.wait(5 * 60 * 1000);
 513                     }
 514                 }
 515             } catch (InterruptedException e) { Log.warn(this, e); }
 516         }
 517     }
 518
 519     public static InetAddress[] getMailExchangerIPs(String hostName) {
 520         InetAddress[] ret;
 521         try {
 522             Hashtable env = new Hashtable();
 523             env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
 524             DirContext ictx = new InitialDirContext(env);
 525             Attributes attrs = ictx.getAttributes(hostName, new String[] { "MX" });
 526             Attribute attr = attrs.get("MX");
 527             if (attr == null) {
 528                 ret = new InetAddress[1];
 529                 try {
 530                     ret[0] = InetAddress.getByName(hostName);
 531                     if (ret[0].equals(IP.getIP(127,0,0,1)) || ret[0].isLoopbackAddress()) throw new UnknownHostException();
 532                     return ret;
 533                 } catch (UnknownHostException uhe) {
 534                     Log.warn(SMTP.class, "no MX hosts or A record for " + hostName);
 535                     return new InetAddress[0];
 536                 }
 537             } else {
 538                 ret = new InetAddress[attr.size()];
 539                 NamingEnumeration ne = attr.getAll();
 540                 for(int i=0; ne.hasMore();) {
 541                     String mx = (String)ne.next();
 542                     // FIXME we should be sorting here
 543                     mx = mx.substring(mx.indexOf(" ") + 1);
 544                     if (mx.charAt(mx.length() - 1) == '.') mx = mx.substring(0, mx.length() - 1);
 545                     InetAddress ia = InetAddress.getByName(mx);
 546                     if (ia.equals(IP.getIP(127,0,0,1)) || ia.isLoopbackAddress()) continue;
 547                     ret[i++] = ia;
 548                 }
 549             }
 550         } catch (Exception e) {
 551             Log.warn(SMTP.class, "couldn't find MX host for " + hostName + " due to");
 552             Log.warn(SMTP.class, e);
 553             return new InetAddress[0];
 554         }
 555         return ret;
 556     }
 557 }