zimbra generates occasional duplicate message

[ljm]

We seem to be seeing the occasional duplicate message - using zcs-NETWORK-4.0.4_GA_457.RHEL4 trial.

Here's an example.

Postfix recieves one message:
/var/log/zimra.log
Jan 15 17:11:29 fred postfix/smtpd[25400]: connect from example.com[1.2.3.4]
Jan 15 17:11:29 fred postfix/smtpd[25400]: 264065C5D9: client=example.com[1.2.3.4]
Jan 15 17:11:29 fred postfix/cleanup[25404]: 264065C5D9: message-id=<90084D0257CC5E428938C833C55C849EEB195E@blah.ex ample.com>
Jan 15 17:11:29 fred postfix/qmgr[18630]: 264065C5D9: from=<a.b@example.com>, size=7850, nrcpt=1 (queue active)
Jan 15 17:11:29 fred postfix/smtpd[25400]: disconnect from example.com[1.2.3.4]
Jan 15 17:11:29 fred postfix/lmtp[25405]: 264065C5D9: to=<c.d@recipient.com>, relay=internal.example.com[192.168.1.2], delay=0, status=sent (250 2.1.5 OK)
Jan 15 17:11:29 fred postfix/qmgr[18630]: 264065C5D9: removed

So far so good. Then in /opt/zimbra/log/zimbra.log:
2007-01-15 17:11:29,187 INFO [LmtpServer-144] [] LmtpHandler - [192.168.1.2] connected
2007-01-15 17:11:29,286 INFO [LmtpServer-144] [name=c.d@recipient.com;] FileBlobStore - Stored size=7850 wrote=7850 path=/opt/zimbra/store/incoming/1168584106108-252.msg vol=1 digest=I467LrZ+GnHFxMv8I3kMXXgZD7I=
2007-01-15 17:11:29,287 INFO [LmtpServer-144] [name=c.d@recipient.com;] FileBlobStore - Renamed id=29817 mbox=6 oldpath=/opt/zimbra/store/incoming/1168584106108-252.msg newpath=/opt/zimbra/store/0/6/msg/7/29817-34962.msg
2007-01-15 17:11:29,316 INFO [LmtpServer-144] [name=c.d@recipient.com;] mailbox - Added message id=29817 digest=I467LrZ+GnHFxMv8I3kMXXgZD7I= mailbox=6 rcpt=c.d@recipient.com
2007-01-15 17:12:09,254 INFO [Timer-0] [] FileUploadServlet - 1 pending file uploads
2007-01-15 17:12:23,781 INFO [IndexWritersSweeper] [] MailboxIndex - open index writers sweep: before=1, closed=0, after=1 (0ms)
2007-01-15 17:13:00,006 INFO [http-443-Processor100] [mid=6;ip=192.168.2.222;name=c.d@recipient.com;] FileBlobStore - Stored size=6057 wrote=6057 path=/opt/zimbra/store/incoming/1168584106108-253.msg vol=1 digest=OILd,YwQ1nFtWdp1tKQbSMy9iQk=
2007-01-15 17:13:00,006 INFO [http-443-Processor100] [mid=6;ip=192.168.2.222;name=c.d@recipient.com;] FileBlobStore - Renamed id=29818 mbox=6 oldpath=/opt/zimbra/store/incoming/1168584106108-253.msg newpath=/opt/zimbra/store/0/6/msg/7/29818-34965.msg
2007-01-15 17:13:00,039 INFO [http-443-Processor100] [mid=6;ip=192.168.2.222;name=c.d@recipient.com;] mailbox - Added message id=29818 digest=OILd,YwQ1nFtWdp1tKQbSMy9iQk= mailbox=6 rcpt=:API:

And sure enough, we end up with two files:
/opt/zimbra/store/0/6/msg/7/29817-34962.msg
/opt/zimbra/store/0/6/msg/7/29818-34965.msg

which are copies of one another except that the second one has a different Message-ID and all it's "Received" headers have been removed.

Could this be some kind of misconfiguration our end? An issue with the outlook connector?