Hey Zimbra support guy. I agree. I'm currently running Outlook and MYOB using MAPI to send emails I started a case with you guys and am logging everything and doing everything I can to reproduce the problem. But I haven't had it again!!
Anyone else there please get some logs in :-)
Log Zimbra whilst reproducing.
tail -f /opt/zimbra/log/mailbox.log
Also, log Outlook. (from the Wiki)
Outlook Troubleshooting Options - Zimbra :: Wiki
ZCOLogCtl.exe is installed when ZCS Connector for Outlook is installed. This logging control tool is in the \Program files\common files\system\msmapi\1033 directory.
It's funny that I'm unable to reproduce it when I need it to error. Hope you all have better(?) luck.