David Hrbáč wrote: > Well, I do not understand it now. > > domain.tld has: > mx 20 some_server2 > mx 10 some_server1 The problem occurs on domain.tld == some_server1, which is a mail server. domain.tld does backups for some_server2.tld and vice versa. so, domain.tld has: mx 20 some_server2.tld (so, they do backup in case our server is down) mx 10 domain.tld (this server. should deliver mails for domain.tld) if some_server2.tld (which for we are doing mx backup as well) is down, our system keeps mails but does not deliver them. BUT: (and that's the problem) if one of us here on domain.tld wants to send an email to some_server2.tld, then this problem with 'loops back to me' occurs (since centos update). so IMO, it is correct having postmap -q some_server2.tld mysql:/etc/postfix/sql/transport returning smtp:some_server2.tld and postmap -q domain.tld mysql:/etc/postfix/sql/transport returning maildrop: so, if mails for some_server2.tld are arriving at domain.tld, it tries to forward them via smtp to some_server2.tld which should be done via: smtp inet n - n - 25 smtpd (from master.cf), AFAIK and EVEN, if I REMOVE the mysql entry for smtp:some_server2.tld, so it should appear to postfix like every other domain in the world, postfix finds a loop back to itself. And that's, what I don't understand. This configuration was already working and productive. thorsten.