I upgraded from 6.0.7 to 6.0.9 and couldn't send or receive mail. I got errors in /opt/zimbra/log/mailbox.log like those below:


Code:
com.zimbra.common.service.ServiceException: system failure: Unable to send message
ExceptionId:btpool0-30://mail.flec.tv/service/soap/SendMsgRequest:1292834684764:23b4ce15501674a6
Code:service.FAILURE
	at com.zimbra.common.service.ServiceException.FAILURE(ServiceException.java:248)
	at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:477)
	at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:309)
	at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:266)
	at com.zimbra.cs.service.mail.SendMsg.doSendMessage(SendMsg.java:189)
	at com.zimbra.cs.service.mail.SendMsg.handle(SendMsg.java:150)
	at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEngine.java:420)
	at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:274)
	at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:158)
	at com.zimbra.soap.SoapServlet.doWork(SoapServlet.java:291)
	at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:212)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:181)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
	at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(SetHeaderFilter.java:79)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
	at org.mortbay.servlet.UserAgentFilter.doFilter(UserAgentFilter.java:81)
	at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter.java:155)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:218)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
	at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
	at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.handler.rewrite.RewriteHandler.handle(RewriteHandler.java:230)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.handler.DebugHandler.handle(DebugHandler.java:77)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:543)
	at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:939)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:413)
	at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:451)
Caused by: com.zimbra.cs.mailbox.MailSender$SafeMessagingException: Exception reading response; chained exception is:
	java.net.SocketTimeoutException: Read timed out
	at com.sun.mail.smtp.SMTPTransport.readServerResponse(SMTPTransport.java:1764)
	at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1523)
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:453)
	at javax.mail.Service.connect(Service.java:291)
	at javax.mail.Service.connect(Service.java:172)
	at javax.mail.Service.connect(Service.java:121)
	at com.zimbra.cs.mailbox.MailSender.sendMessageToHost(MailSender.java:781)
	at com.zimbra.cs.mailbox.MailSender.sendMessage(MailSender.java:702)
	at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:412)
What was most helpful was in the /var/log/maillog:

Code:
Dec 20 00:02:07 mail postfix/showq[6997]: fatal: match_list_parse: open file /opt/zimbra/postfix-2.6.7.2z/conf/localdomains: No such file or directory
It turns out that when Zimbra upgraded postfix it failed to create the localdomains file (an empty file). This caused Postfix to crash, and stop listening on port 25.

Creating the localdomains file and restarting the services with zmcontrol fixed the problem, hope this helps others out there.