Hello I already asked in the IRC, but apart from recommendations reading the mailing lists, nobody could help me. I read all postfix-update related articles but non of them seemed to match or resolve my problem: Everything works fine, apart from one host, which we are doing MX backups for (backupdomain.com): Sep 22 12:18:58 homer postfix/smtp[18784]: 6BD7B1189E4: to=<user at backupdomain.com>, relay=none, delay=53, status=bounced (mail for backupdomain.com loops back to myself) Sep 22 12:18:58 homer postfix/cleanup[18791]: B3DD6118A13: message-id=<20060922111858.B3DD6118A13 at mail.mydomain.com> Sep 22 12:18:58 homer postfix/qmgr[18776]: B3DD6118A13: from=<>, size=2758, nrcpt=1 (queue active) Sep 22 12:18:58 homer postfix/qmgr[18776]: 6BD7B1189E4: removed The backup MX in our domain record for the backupdomain has priority 20, we 10. dig MX mydomain.com mydomain.com. 86400 IN MX 20 mail.backupdomain.com. mydomain.com. 86400 IN MX 10 mail.mydomain.com. postfix's transport_map is configured to use mysql. a postmap -q backupdomain.com mysql:/etc/postfix/sql/transport returns: smtp:mail.backupdomain.com so it was forwarding a message to that domain. That worked fine. After the postfix upgrade, this stopped working. The target the error, I removed the smtp:mail.backupdomain.com entry from the mysql table and also removed the MX entry for the backupdomain, which I was told, could cause problems as well. It still says: mail for backupdomain.com loops back to myself. So, I am wondering, where postfix gets this information from? Can you give me some further advise? thx, thorsten.