Wrong DNS configuration. Which?
Someone has been failing to connect to my sendmail for several days. My syslog is full with error messages:
Mar 1 08:29:08 lee sendmail: f213T8o01042: ruleset=check_mail, arg1=<email@example.com>, relay=server.tgngu.tyumen.ru [184.108.40.206] (may be forged), reject=451 4.1.8 <firstname.lastname@example.org>... Domain of sender address email@example.com does not resolve
Mar 1 08:29:08 lee sendmail: f213T8o01042: from=<firstname.lastname@example.org>, size=272074, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=server.tgngu.tyumen.ru [220.127.116.11] (may be forged)
I'm not very experienced with bind, but so far as I understand something's wrong with either my DNS configuration or with the other side's. I believe it isn't mine. I get a lot of mail daily without problem (for example, from this list). On the other hand when I try `dig tgngu.tyumen.ru ANY' I don't see any A-record.
Am I right, that sendmail's check_mail rejects connection because there are no A-record for tgngu.tyumen.ru in other side DNS configuration?
Is it right address: 18.104.22.168.tyumen.ru. (I saw it in output of `dig tgngu.tyumen.ru ANY')?
May it be someone's trying to hack me?
I use Debian Linux unstable (kernel 2.4.2, libc6 2.2.2), bind 9.1.0, sendmail 8.11.2.
Thank you Mikhail.