I checked ISPC 188.8.131.52 and this user exist! Yet I get this in the logfiles. Authtest works correct as well as some postmap tests, It seems the issue is with the relay=maildrop permissions? In the code part I highlited the error by adding spaces around the line. Code: # cat /var/log/syslog |grep 441D01A06148 Aug 27 15:46:52 artemis postfix/smtpd: 441D01A06148: client=localhost[127.0.0.1] Aug 27 15:46:52 artemis postfix/cleanup: 441D01A06148: message-id=<[email protected]> Aug 27 15:46:52 artemis postfix/qmgr: 441D01A06148: from=<[email protected]>, size=3615, nrcpt=1 (queue active) Aug 27 15:46:53 artemis amavis: (16097-17) Passed CLEAN, [184.108.40.206] [220.127.116.11] <[email protected]> -> <[email protected]>, Message-ID: <[email protected]>, mail_id: sWX3Yp38I5m8, Hits: 0.332, size: 3133, queued_as: 441D01A06148, 14690 ms Aug 27 15:46:53 artemis postfix/pipe: 441D01A06148: to=<[email protected]>, relay=maildrop, delay=0.76, delays=0.05/0.1/0/0.61, dsn=5.1.1, status=bounced (user unknown. Command output: ERR: authdaemon: s_connect() failed: Permission denied Invalid user specified. ) Aug 27 15:46:53 artemis postfix/bounce: 441D01A06148: sender non-delivery notification: 122591A06171 Aug 27 15:46:53 artemis postfix/qmgr: 441D01A06148: removed Aug 27 15:46:53 artemis postfix/smtp: 27FEA1A06146: to=<[email protected]>, relay=127.0.0.1[127.0.0.1]:10024, delay=50, delays=33/0.02/4.1/13, dsn=2.0.0, status=sent (250 2.0.0 Ok, id=16097-17, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as 441D01A06148) Were is this permission problem? How could it change - this was an perfectly working installation. maybe caused by an apt-get upgrade?