Error when sending email with attachement

[khchong]

I notice the error "FileUploadServlet - Unable to store upload." in the mailbox.log is happened quite frequently.
It is usually happens when user having the email with large attachment (2mb - 10mb).
User takes up to 20-30 minutes to send an email.

Did anyone encounter the same problem as me? What is the likely cause of this error?

Below is the details of the error message:-
2011-09-23 14:44:17,964 WARN [btpool0-3120://mail.example.com/service/upload?fmt=raw] [name=test@example.com;mid=93;ip=101.109.208.100;ua =Jakarta Commons-HttpClient/3.1;] FileUploadServlet - Unable to store upload. Deleting name=msg-1073742393, StoreLocation=/opt/zimbra/data/tmp/upload/upload__5ff3b771_13287783026__8000_00005265.tmp, size=212992bytes, isFormField=false, FieldName=upload
org.mortbay.jetty.EofException
at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:319)
at org.mortbay.jetty.HttpParser$Input.blockForContent (HttpParser.java:1161)
at org.mortbay.jetty.HttpParser$Input.read(HttpParser .java:1122)
at com.zimbra.common.util.ByteUtil.copy(ByteUtil.java :668)
at com.zimbra.cs.service.FileUploadServlet.handlePlai nUpload(FileUploadServlet.java:581)
at com.zimbra.cs.service.FileUploadServlet.doPost(Fil eUploadServlet.java:459)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:725)
at com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:208)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:814)
at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1166)
at com.zimbra.cs.servlet.SetHeaderFilter.doFilter(Set HeaderFilter.java:79)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at org.mortbay.servlet.UserAgentFilter.doFilter(UserA gentFilter.java:81)
at org.mortbay.servlet.GzipFilter.doFilter(GzipFilter .java:155)
at org.mortbay.jetty.servlet.ServletHandler$CachedCha in.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:218)
at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:422)
at org.mortbay.jetty.handler.ContextHandlerCollection .handle(ContextHandlerCollection.java:230)
at org.mortbay.jetty.handler.HandlerCollection.handle (HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152)
at org.mortbay.jetty.handler.rewrite.RewriteHandler.h andle(RewriteHandler.java:230)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152)
at org.mortbay.jetty.handler.DebugHandler.handle(Debu gHandler.java:77)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:543)
at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:946)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:756)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:405)
at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:410)
at org.mortbay.thread.BoundedThreadPool$PoolThread.ru n(BoundedThreadPool.java:451)