As we updated from 7.0 to current 7.1 witch latest patch some outllook clients got the same...
<SyncError><Request><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Header><context xmlns="urn:zimbra"><userAgent name="ZimbraConnectorForOutlook" version="7.1.1.6324"/><nonotify/><noqualify/><account by="id">63641b8f-6140-4061-89dc-dfda6b24eb51</account><authToken>0_f0fd2fc406c626bdd025c5dd880bf b298cf75365_69643d33363a36333634316238662d36313430 2d343036312d383964632d6466646136623234656235313b65 78703d31333a313331303230363432393335363b747970653d 363a7a696d6272613b</authToken><nosession/></context></soap:Header><soap:Body><SaveDraftRequest xmlns="urn:zimbraMail"><m aid="20a78a5b-72c6-4184-866c-fa8a35449a3d:6711474b-6b43-4ea6-9fda-2ccdffb38f36" id="132241"/></SaveDraftRequest></soap:Body></soap:Envelope></Request><Response><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Header><context xmlns="urn:zimbra"><change token="369525"/></context></soap:Header><soap:Body><soap:Fault><soap:Code><soa p:Value>soap:Sender</soap:Value></soap:Code><soap:Reason><soap:Text>cannot modify immutable object: 132241</soap:Text></soap:Reason><soap

etail><Error xmlns="urn:zimbra"><Code>mail.IMMUTABLE_OBJECT</Code><Trace>com.zimbra.cs.mailbox.MailServiceExcep tion: cannot modify immutable object: 132241
ExceptionId:btpool0-635://$DOMAIN/service/soap/SaveDraftRequest:1310033655076:db2846fe9fbc85ec
Code:mail.IMMUTABLE_OBJECT Arg

itemId, IID, "132241")
at com.zimbra.cs.mailbox.MailServiceException.IMMUTAB LE_OBJECT(MailServiceException.java:383)
at com.zimbra.cs.mailbox.Mailbox.saveDraftInternal(Ma ilbox.java:5129)
at com.zimbra.cs.mailbox.Mailbox.saveDraft(Mailbox.ja va:5080)
at com.zimbra.cs.service.mail.SaveDraft.handle(SaveDr aft.java:126)
at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEng ine.java:412)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:287)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:158)
at com.zimbra.soap.SoapServlet.doWork(SoapServlet.jav a:294)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.jav a:215)
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)
</Trace><a t="IID" n="itemId">132241</a></Error></soap

etail></soap:Fault></soap:Body></soap:Envelope></Response></SyncError>