>> Thanks. So my understanding is correct that Postfix gets the hostnames you
> see in the logs from PTR records? > > Yes. > >> You are saying that additionally, if the A record for the domain > doesn't match the client IP, the PTR will be ignored and thus you'll > still get "unknown"? > > No, the A record for whatever name that the PTR returned, as with the > examples above. Sorry, that's what I meant by "the domain" -- rather, the host name that the PTR lookup gives you. >> In my case, my PTR and A records look good, and online tools (mxtoolbox, > etc) seem to verify this. The "dig" command comes back looking good > as well. Yet, I keep getting "connect from unknown" (from my server, > but others, like email coming from gmail work correctly). I will have to > assume > that there is some kind of glitch in the DNS lookups Postfix is doing for my > domain/host. > > "connect from unknown" in YOUR logs has nothing to do with YOUR DNS > entries. It has to do with the DNS entries for the remote system that's > connecting to yours. Again, my language mistakes. I am testing using two separate machines. The *client* that is connecting has correct PTR and matching A record for the host name that comes back in the PTR (tests run on the server side, using "dig" or "host"), but... Ahh-ha. The host/domain *IS* recognized as expected. My issue was that when connecting to a port used for reinjecting externally filtered mail, I get "connect from unknown" - presumably because the listener is not doing DNS lookups. -o smtpd_peername_lookup=no Thanks for the pointers, very much appreciate your time
