Outlook won't send emails (or meeting requests) even though the sync finishes successfully.

Here's what the /opt/zimbra/log/zimbra.log records:

2006-11-19 18:53:14,375 INFO [http-443-Processor100] [mid=10;ip=10.8.0.6;name=vshah@mydomain.com;] SoapEngine - handler exception
com.zimbra.cs.mailbox.MailServiceException$NoSuchI temException: no such message:
-2147221233
at com.zimbra.cs.mailbox.MailServiceException.NO_SUCH _MSG(MailServiceExc
eption.java:150)
at com.zimbra.cs.mailbox.MailItem.noSuchItem(MailItem .java:821)
at com.zimbra.cs.mailbox.Mailbox.getItemById(Mailbox. java:1829)
at com.zimbra.cs.mailbox.Mailbox.move(Mailbox.java:37 26)
at com.zimbra.cs.operation.ItemActionOperation.callba ck(ItemActionOperat
ion.java:304)
at com.zimbra.cs.operation.Operation.schedule(Operati on.java:190)
at com.zimbra.cs.operation.ItemActionOperation.UPDATE (ItemActionOperatio
n.java:147)
at com.zimbra.cs.service.mail.ItemAction.handleCommon (ItemAction.java:16
5)
at com.zimbra.cs.service.mail.MsgAction.handle(MsgAct ion.java:50)
at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEng ine.java:261)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:162)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:84)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.jav a:223)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:709)
at com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:173)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:802)
at org.apache.catalina.core.ApplicationFilterChain.in ternalDoFilter(Appl
icationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.do Filter(ApplicationF
ilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invo ke(StandardWrapperV
alve.java:213)
at org.apache.catalina.core.StandardContextValve.invo ke(StandardContextV
alve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke( StandardHostValve.j
ava:126)
at org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.j
ava:105)
at org.apache.catalina.core.StandardEngineValve.invok e(StandardEngineVal
ve.java:107)
at org.apache.catalina.valves.AccessLogValve.invoke(A ccessLogValve.java:
541)
at org.apache.catalina.connector.CoyoteAdapter.servic e(CoyoteAdapter.jav
a:148)
at org.apache.coyote.http11.Http11Processor.process(H ttp11Processor.java
:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11 ConnectionHandler.p
rocessConnection(Http11BaseProtocol.java:667)
at org.apache.tomcat.util.net.PoolTcpEndpoint.process Socket(PoolTcpEndpo
int.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThr ead.runIt(LeaderFol
lowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlR unnable.run(ThreadP
ool.java:684)
at java.lang.Thread.run(Thread.java:595)
2006-11-19 18:54:15,747 INFO [http-443-Processor100] [mid=10;ip=10.8.0.6;name=vshah@mydomain.com;] SoapEngine - handler exception

Outlook was working fine for about 2 days. I installed the ZCO on Friday.

Any ideas?

[BTW: I wish the ZCO installer would check to make sure that Outlook was the default email client before trying to install. If Outlook isn't the default mail client, it still installs but things don't work right.]