April 23rd, 2013, 08:48 PM
Postfix "abuse"; what's the problem?
I discovered today that hotmail isn't accepting emails from my server and while I'm not 100% sure this is why, I did find it in passing: Apparently I'm blacklisted by Backscatterer.
Note that I did have a lot of problems many months ago which lead to a complete reconfiguration of my mail server, now using postfix. Relaying should now be forbidden except when delivering to local accounts, and the SMTP server requires authentication to send. This seemed to work for quite some time.
But now I'm told there was a problem that caused it to be blacklisted again, and it pointed to this time period in my logs.
I'm not seeing any problem in the logs there...
Apr 14 04:23:57 domain postfix/smtpd: warning: 18.104.22.168: address not listed for hostname host135.ten.icentr.net
Apr 14 04:23:57 domain postfix/smtpd: connect from unknown[22.214.171.124]
Apr 14 04:24:02 domain postfix/smtpd: NOQUEUE: reject: RCPT from unknown[126.96.36.199]: 550 5.1.1 <email@example.com>: Recipient address rejected: User unknown in virtual mailbox table; from=<firstname.lastname@example.org> to=<email@example.com> proto=SMTP helo=<yahoo.com>
Apr 14 04:24:03 domain postfix/smtpd: lost connection after RCPT from unknown[188.8.131.52]
Apr 14 04:24:03 domain postfix/smtpd: disconnect from unknown[184.108.40.206]
Am I missing something? It looks like a typical bad-recipient rejection
April 24th, 2013, 09:55 AM
It is not common, but some receivers will verify the sender by doing a reverse lookup on the connecting server and verify that the forward lookup agrees. In your case the reverse lookup shows:
host135.ten.icentr.net. However, a forward lookup on that name gives a name error.
Also be aware that hotmail uses DMARC, although there is no message to indicate that it failed a DMARC check.
April 24th, 2013, 02:29 PM
Thanks for the reply.
Originally Posted by couttsj
I set up a @hotmail.com account of my own and was able to receive the email fine on that, and it was already working for gmail and some other domains, so I don't think Backscatterer is actually actually harming anything.
I also set up SPF entries on my DNS which is maybe helping.