Since more than a year i have the problem, that ZDesktop does not send emails with bigger attachments or bigger HTML content. Emails keep in the Outbox until i send another small email to myself. The max upload size should not be the problem. If i use the webclient, everything works as expected.

In zdesktop i found some older error reports:

Code:
Product name:    Zimbra Desktop
Product version: 7.2.2
Build ID:        11951
Release type:    GA
OS Platform:     Mac OS X i386 10.8.3
Time of event:   2013-04-18 13:42:44
Error type:      zclient.UPLOAD_FAILED
Item ID:         40792
Error summary:   push item failed

Failure details - PLEASE REMOVE ANY SENSITIVE INFORMATION
----------------------------------------------------------------------------

com.zimbra.common.zclient.ZClientException: Attachment post failed, status=413
ExceptionId:btpool0-7793:1366285364691:ceb8c3025e331c3c
Code:zclient.UPLOAD_FAILED
        at com.zimbra.common.zclient.ZClientException.UPLOAD_FAILED(ZClientException.java:57)
        at com.zimbra.cs.zclient.ZMailbox.uploadContentAsStream(ZMailbox.java:1918)
        at com.zimbra.cs.mailbox.PushChanges.uploadMessage(PushChanges.java:472)
        at com.zimbra.cs.mailbox.PushChanges.syncMessage(PushChanges.java:1268)
        at com.zimbra.cs.mailbox.PushChanges.sync(PushChanges.java:306)
        at com.zimbra.cs.mailbox.PushChanges.sync(PushChanges.java:195)
        at com.zimbra.cs.mailbox.MailboxSync.sync(MailboxSync.java:193)
        at com.zimbra.cs.mailbox.ZcsMailbox.sync(ZcsMailbox.java:124)
        at com.zimbra.cs.service.offline.OfflineSync.handle(OfflineSync.java:55)
        at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEngine.java:412)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:287)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:158)
        at com.zimbra.soap.SoapServlet.doWork(SoapServlet.java:303)
        at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:217)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
        at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:206)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:814)
        at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
        at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:390)
        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:422)
        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.Server.handle(Server.java:326)
        at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:585)
        at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:988)
        at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
        at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
        at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:415)
        at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:429)
        at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:451)

----------------------------------------------------------------------------
I'm using ZCS 8.0.4 GA at the moment on Ubuntu 12.04, but also had this issue earlier. Any ideas?

TheChief