Outlook appointment invitation problem

[PNE]

Using 3.1.4 OSS on Centos 4.3. When I create an appointment in Outlook XP and invite another person, Outlook sends (I suppose specially formatted) invitation message. When this message is send through Zimbra server, it bounces back with this postfix error:

<invited_user@domain.com>: host mail.domain.com[172.20.1.150] said: 554 5.0.0 Permanent
message delivery failure (in reply to end of DATA command)

There is no Exchange server, OSS Zimbra only, no Outlook connector, Outlook is Czech version. No requirement to store appointment in Zimbra server. Just simple information exchange between two Outlooks.

Anybody seen that? How could it be solved? It looks like persistent bug, it can be reproduced anytime.

[PNE]

Update: described bug is not persistent, just occassional, as further testing showed.

[dkarp]

Anything in zimbra.log?

[PNE]

Here comes the portion of zimbra.log. Real domain names were replaced with domain.com or local.domain.com respectively.

Undelivered.zip attachment is the message in Outlook msg format as it has been bounced back by Zimbra. This is not the same case as the one in log.

[msvangren]

I'm experiencing the same problem with 4.5.9 NE. Has anyone found a solution for this yet?

For some reason, appointment invitations from Outlook bounce, even though amavisd has marked them as clean:

Nov 19 09:26:09 mail postfix/smtpd[9439]: connect from mail.sender.tld[12.34.56.78]
Nov 19 09:26:10 mail postfix/smtpd[9439]: 242C01F08754: client=mail.sender.tld[12.34.56.78]
Nov 19 09:26:10 mail postfix/cleanup[12248]: 242C01F08754: message-id=<17438A50FC2804469EEDA28B4D82655B022204D5@mail-01.sender.tld>
Nov 19 09:26:10 mail postfix/qmgr[15544]: 242C01F08754: from=<from.user@sender.tld>, size=3905, nrcpt=1 (queue active)
Nov 19 09:26:10 mail postfix/smtpd[9439]: disconnect from mail.sender.tld[12.34.56.78]
Nov 19 09:26:10 mail amavis[11815]: (11815-16) ESMTP::10024 /opt/zimbra/amavisd/tmp/amavis-20071119T082007-11815: <from.user@sender.tld> -> <tou@recipient.tld> SIZE=3905 BODY=8BITMIME Received: from mail.recipient.tld ([127.0.0.1]) by localhost (mail.recipient.tld [127.0.0.1]) (amavisd-new, port 10024) with ESMTP for <tou@recipient.tld>; Mon, 19 Nov 2007 09:26:10 +0100 (CET)
Nov 19 09:26:10 mail amavis[11815]: (11815-16) Checking: LZXk8RzfpLSe [12.34.56.78] <from.user@sender.tld> -> <tou@recipient.tld>
Nov 19 09:26:13 mail postfix/smtpd[12289]: connect from localhost.localdomain[127.0.0.1]
Nov 19 09:26:13 mail postfix/smtpd[12289]: 485811F08755: client=localhost.localdomain[127.0.0.1]
Nov 19 09:26:13 mail postfix/cleanup[11753]: 485811F08755: message-id=<17438A50FC2804469EEDA28B4D82655B022204D5@mail-01.sender.tld>
Nov 19 09:26:13 mail postfix/smtpd[12289]: disconnect from localhost.localdomain[127.0.0.1]
Nov 19 09:26:13 mail postfix/qmgr[15544]: 485811F08755: from=<from.user@sender.tld>, size=4495, nrcpt=1 (queue active)
Nov 19 09:26:13 mail amavis[11815]: (11815-16) FWD via SMTP: <from.user@sender.tld> -> <tou@recipient.tld>,BODY=8BITMIME 250 2.6.0 Ok, id=11815-16, from MTA([127.0.0.1]:10025): 250 Ok: queued as 485811F08755
Nov 19 09:26:13 mail amavis[11815]: (11815-16) Passed CLEAN, [12.34.56.78] [12.34.56.78] <from.user@sender.tld> -> <tou@recipient.tld>, Message-ID: <17438A50FC2804469EEDA28B4D82655B022204D5@mail-01.sender.tld>, mail_id: LZXk8RzfpLSe, Hits: -2.598, size: 3905, queued_as: 485811F08755, 2977 ms
Nov 19 09:26:13 mail postfix/smtp[12279]: 242C01F08754: to=<tou@recipient.tld>, orig_to=<to.user@recipient.tld>, relay=127.0.0.1[127.0.0.1], delay=3, status=sent (250 Ok: queued as 485811F08755)
Nov 19 09:26:13 mail postfix/qmgr[15544]: 242C01F08754: removed
Nov 19 09:26:13 mail postfix/lmtp[11759]: 485811F08755: to=<tou@recipient.tld>, relay=mail.recipient.tld[98.76.54.32], delay=0, status=bounced (host mail.recipient.tld[98.76.54.32] said: 554 5.0.0 Permanent message delivery failure (in reply to end of DATA command))

(real e-mail addresses, host names and IP addresses have been replaced)

Any ideas?