Viktor Dukhovni via Postfix-users:
> On Tue, Oct 21, 2025 at 04:59:20PM +0200, Antonin Verrier via Postfix-users
> wrote:
>
> > Le 21 octobre 2025 08:52:23 GMT+02:00, Antonin Verrier via Postfix-users
> > <[email protected]> a ?crit?:
> > >See this log line for example:
> > >
> > >2025-10-20T00:27:12.626227+02:00 mail postfix/mx/smtpd[226824]: warning:
> > >Unable to look up MX host irondelle.o2switch.net for Sender address
> > >[email protected]: Name or service not known
> >
> > I've just realized something... If I have the above line in my logs,
> > doesn't that mean the A lookup for the MX is happening already anyway
> > ?
> >
> > I have also check_sender_mx_access restriction in place so maybe it comes
> > from there.
>
> Yes, it appears that check_sender_mx_access performs table lookups for
> each MX host, not just by name, but also by its IP addresses. FWIW, I
> don't think this is a good idea, I would have limited the lookup keys
> to just the hostnames which are returned in a single DNS query.
Well, to implement access by IP address, one needs to look up an
IP address. This has been very useful to deflect mail from spammers
that run tons of short-lived domains from the same infrastructure.
Wietse
_______________________________________________
Postfix-users mailing list -- [email protected]
To unsubscribe send an email to [email protected]
