Ubuntu:
postfix/cleanup
postfix/qmgr
postfix/amavis/smtp
postfix/pipe
postfix/error
postfix/bounce
postfix/smtpd
Sep 25 11:11:11 server postfix/smtpd[1234]: connect from unknown[10.10.10.11]
Sep 25 11:11:11 server postfix/smtpd[1234]: connect from server.example.com[10.10.10.12]
See also