I configured the Zimbra Network edition (8.0.4) on RHEL with no problems. We placed it in production yesterday. When users started using the server, an issue started to come up.

When either using the web client or the Outlook connector there is an error when sending email. The error occurs sporadically -- once every few times an email is sent. I am getting a timeout connecting to port 25. For example:

In this listing:
{external IP removed} = the proper IP address from the web client
{internal IP removed} = the proper internal IP address of the Zimbra server
{email removed} = the email address attempting to send an email

In the /opt/zimbra/log/mailbox.log:

2013-08-20 14:54:37,519 INFO [qtp695716855-94117:https://{internal IP removed}:443/se...endMsgRequest] [name={email removed};mid=3;ip={external IP removed};ua=ZimbraWebClient - GC28 (Mac)/8.0.4_GA_5737;] SoapEngine - handler exception
com.zimbra.common.service.ServiceException: system failure: Unable to send message
ExceptionId:qtp695716855-94117:https://{internal IP removed}:443/service/soap/SendMsgRequest:1377024877519:568a29421643160f
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:258)
at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(M ailSender.java:692)
at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(M ailSender.java:448)
at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(M ailSender.java:403)
at com.zimbra.cs.service.mail.SendMsg.doSendMessage(S endMsg.java:234)
at com.zimbra.cs.service.mail.SendMsg.handle(SendMsg. java:166)
at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEng ine.java:522)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:385)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:258)
at com.zimbra.soap.SoapServlet.doWork(SoapServlet.jav a:293)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.jav a:209)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:727)
at com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:208)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:820)
at org.eclipse.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:652)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1320)
at com.zimbra.cs.servlet.RequestStringFilter.doFilter (RequestStringFilter.java:52)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(Set HeaderFilter.java:57)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at org.eclipse.jetty.servlets.UserAgentFilter.doFilte r(UserAgentFilter.java:82)
at org.eclipse.jetty.servlets.GzipFilter.doFilter(Gzi pFilter.java:256)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at com.zimbra.cs.servlet.ETagHeaderFilter.doFilter(ET agHeaderFilter.java:45)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at com.zimbra.cs.servlet.ZimbraQoSFilter.doFilter(Zim braQoSFilter.java:114)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at org.eclipse.jetty.servlets.DoSFilter.doFilterChain (DoSFilter.java:473)
at org.eclipse.jetty.servlets.DoSFilter.doFilter(DoSF ilter.java:344)
at org.eclipse.jetty.servlets.DoSFilter.doFilter(DoSF ilter.java:315)
at org.eclipse.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1291)
at org.eclipse.jetty.servlet.ServletHandler.doHandle( ServletHandler.java:443)
at org.eclipse.jetty.server.handler.ScopedHandler.han dle(ScopedHandler.java:137)
at org.eclipse.jetty.security.SecurityHandler.handle( SecurityHandler.java:556)
at org.eclipse.jetty.server.session.SessionHandler.do Handle(SessionHandler.java:227)
at org.eclipse.jetty.server.handler.ContextHandler.do Handle(ContextHandler.java:1044)
at org.eclipse.jetty.servlet.ServletHandler.doScope(S ervletHandler.java:372)
at org.eclipse.jetty.server.session.SessionHandler.do Scope(SessionHandler.java:189)
at org.eclipse.jetty.server.handler.ContextHandler.do Scope(ContextHandler.java:978)
at org.eclipse.jetty.server.handler.ScopedHandler.han dle(ScopedHandler.java:135)
at org.eclipse.jetty.server.handler.ContextHandlerCol lection.handle(ContextHandlerCollection.java:255)
at org.eclipse.jetty.server.handler.HandlerCollection .handle(HandlerCollection.java:154)
at org.eclipse.jetty.server.handler.HandlerWrapper.ha ndle(HandlerWrapper.java:116)
at org.eclipse.jetty.rewrite.handler.RewriteHandler.h andle(RewriteHandler.java:317)
at org.eclipse.jetty.server.handler.DebugHandler.hand le(DebugHandler.java:81)
at org.eclipse.jetty.server.handler.HandlerWrapper.ha ndle(HandlerWrapper.java:116)
at org.eclipse.jetty.server.Server.handle(Server.java :369)
at org.eclipse.jetty.server.AbstractHttpConnection.ha ndleRequest(AbstractHttpConnection.java:486)
at org.eclipse.jetty.server.AbstractHttpConnection.co ntent(AbstractHttpConnection.java:944)
at org.eclipse.jetty.server.AbstractHttpConnection$Re questHandler.content(AbstractHttpConnection.java:1 005)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpPa rser.java:861)
at org.eclipse.jetty.http.HttpParser.parseAvailable(H ttpParser.java:240)
at org.eclipse.jetty.server.AsyncHttpConnection.handl e(AsyncHttpConnection.java:82)
at org.eclipse.jetty.io.nio.SslConnection.handle(SslC onnection.java:196)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.han dle(SelectChannelEndPoint.java:668)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.r un(SelectChannelEndPoint.java:52)
at org.eclipse.jetty.util.thread.QueuedThreadPool.run Job(QueuedThreadPool.java:608)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.r un(QueuedThreadPool.java:543)
at java.lang.Thread.run(Thread.java:722)
Caused by: com.zimbra.cs.mailbox.MailSender$SafeMessagingExce ption: connect timed out; chained exception is:
java.net.SocketTimeoutException: connect timed out
at com.zimbra.cs.mailclient.smtp.SmtpTransport.protoc olConnect(SmtpTransport.java:185)
at javax.mail.Service.connect(Service.java:295)
at javax.mail.Service.connect(Service.java:176)
at javax.mail.Service.connect(Service.java:125)
at com.zimbra.cs.mailbox.MailSender.sendMessageToHost (MailSender.java:1076)
at com.zimbra.cs.mailbox.MailSender.sendMessage(MailS ender.java:1002)
at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(M ailSender.java:617)
... 57 more
2013-08-20 14:54:37,520 INFO [qtp695716855-94117:https://{internal IP removed}:443/service/soap/SendMsgRequest] [name={email removed};mid=3;ip={external IP removed};ua=ZimbraWebClient - GC28 (Mac)/8.0.4_GA_5737;] soap - SendMsgRequest elapsed=60195

The weird part is that this is not a consistent issue. It occurs every other or every third email. The same error occurs with the ajax web client and with the Outlook client.

I have been scouring the forums, support items and the web in general. All of the answers I saw were to a problem like this occurring every time, not sporadically. I opened a support request but their only answer has been to make sure split DNS was running. I do have split DNS running.

Any ideas?