One server I poke around on, has a number of postfix instances
Interestingly, one instance was logging things like :
Oct 26 22:02:05 mail postfix-blah/smtpd: connect from unknown[126.96.36.199] Oct 26 22:02:05 mail postfix-blah/smtpd: CA9292EE2C0: client=unknown[188.8.131.52]
Which makes you think perhaps Postfix isn’t able to do DNS lookups – even though it’s configured to do so.
After a bit of investigation —
- DNS resolution on the host itself works fine.
- Postfix is running smtpd in a chroot (see /etc/postfix-blah/master.cf)
- The ‘default’ Postfix instance (/etc/postfix, /var/spool/postfix) doesn’t have this problem.
- /var/spool/postfix-blah/lib doesn’t exist, but /var/spool/postfix/lib does and contains libnss_* files
- So, cp -a /var/spool/postfix/lib /var/spool/postfix-blah/lib fixes it.
- Turning off ‘chroot’ for the smtp daemon fixes it (edit: /etc/postfix-blah/master.cf).
The server is Ubuntu Lucid, so perhaps it’s a bit long in the tooth now – and maybe this problem won’t crop up for anyone else…