FWIW, here is the complete trace of the zimbra.log when trying to deliver a message to me via LMTP :
Code:
May 5 11:43:40 zimbraserver postfix/postsuper[7047]: Requeued: 1 message
May 5 11:43:58 zimbraserver postfix/pickup[6385]: 2596A4C88C: uid=502 from=<denis@mydomain.com> orig_id=743794C88D
May 5 11:43:58 zimbraserver postfix/cleanup[6392]: 2596A4C88C: message-id=<445B1BA8.6080505@mydomain.com>
May 5 11:43:58 zimbraserver postfix/qmgr[6387]: 2596A4C88C: from=<denis@mydomain.com>, size=3098, nrcpt=1 (queue active)
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) ESMTP::10024 /opt/zimbra/amavisd/tmp/amavis-20060505T114358-04265: <denis@mydomain.com> -> <denis@mydomain.com> Received: SIZE=3098 from zimbraserver.mydomain.com ([127.0.0.1]) by localhost (zimbraserver.mydomain.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 04265-01 for <denis@mydomain.com>; Fri, 5 May 2006 11:43:58 +0200 (CEST)
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) Checking: 8vLb9qD4qj-R [127.0.0.1] <denis@mydomain.com> -> <denis@mydomain.com>
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) cached 68b329da9893e34099c7d8ad5cb9c940 from <denis@mydomain.com> (1,0)
May 5 11:43:58 zimbraserver postfix/smtpd[6461]: connect from localhost.localdomain[127.0.0.1]
May 5 11:43:58 zimbraserver postfix/smtpd[6461]: 55D8D4C88D: client=localhost.localdomain[127.0.0.1]
May 5 11:43:58 zimbraserver postfix/cleanup[6392]: 55D8D4C88D: message-id=<445B1BA8.6080505@mydomain.com>
May 5 11:43:58 zimbraserver postfix/qmgr[6387]: 55D8D4C88D: from=<denis@mydomain.com>, size=4042, nrcpt=1 (queue active)
May 5 11:43:58 zimbraserver postfix/smtpd[6461]: disconnect from localhost.localdomain[127.0.0.1]
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) FWD via SMTP: <denis@mydomain.com> -> <denis@mydomain.com>, 250 2.6.0 Ok, id=04265-01, from MTA([127.0.0.1]:10025): 250 Ok: queued as 55D8D4C88D
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) Passed CLEAN, LOCAL [127.0.0.1] [195.159.43.66] <denis@mydomain.com> -> <denis@mydomain.com>, Message-ID: <445B1BA8.6080505@mydomain.com>, mail_id: 8vLb9qD4qj-R, Hits: -4.319, 245 ms
May 5 11:43:58 zimbraserver postfix/smtp[6404]: 2596A4C88C: to=<denis@mydomain.com>, relay=127.0.0.1[127.0.0.1], delay=18, status=sent (250 2.6.0 Ok, id=04265-01, from MTA([127.0.0.1]:10025): 250 Ok: queued as 55D8D4C88D)
May 5 11:43:58 zimbraserver postfix/qmgr[6387]: 2596A4C88C: removed
May 5 11:43:58 zimbraserver amavis[4265]: (04265-01) extra modules loaded: Net/LDAP/Bind.pm
May 5 11:43:58 zimbraserver postfix/lmtp[6468]: 55D8D4C88D: to=<denis@mydomain.com>, relay=none, delay=0, status=deferred (connect to zimbraserver.mydomain.com[192.168.192.168]: Connection refused)
This was actually after trying to alter the /etc/services file and restarting Zimbra, just to eliminate that as a source of the problem.