Lately it looks like some zombie bot farm is connecting to submission
(and looks to do nothing except connect), causing many of these in the
logs:
Oct 28 06:15:35 mail postfix/smtpd[12941]: warning: hostname x.y.z does
not resolve to address 11.22.33.44: Name or service not known
For submission service where clients often connect from dynamic IP
address ranges, maybe seeing these is not important - just noise, so I
am curious about why postfix is logging this. Does this mean client is
somehow attempting to send before (without) doing any AUTH? I tested by
hand and MAIL FROM result is "530 5.7.0 Must issue a STARTTLS command
first". I found that I neglected to override smtpd_sender_restrictions
in the submission service, but it shouldn't matter if the client cant
AUTH, right?
Or is it default postfix behavior and I can ignore these logs?
