a friend of mine is hosted by a pretty bad service provider and now they couldn't handle his email for more than a week, so I proposed to host his email till he sorts this problem out.
what I did basically was change his DNS entries so that mail.quilombobrasil.com points to my IP and added an MX record for knightsenglish.com pointing towards mail.knightsenglish.com
this works all eprfect his emails started coming onto my server, sending/receiving works perfectly.
BUT now comes the problem. On his .asp website, done years ago by somebody who is no longer available, runs a newsletter whose settigns I can't figure out as I have no idea about ASP.
whenever he sends out his newsletter, my server goes completely crazy and I get all these emails with the following content:
Subject: Postfix SMTP server: errors from hm2223.locaweb.com.br[18.104.22.168]
Transcript of session follows.
Out: 220 h1550830.stratoserver.net ESMTP Postfix (Debian/GNU)
In: EHLO HM2223.locaweb.com.br
Out: 250-AUTH LOGIN PLAIN
Out: 250-AUTH=LOGIN PLAIN
Out: 250 DSN
In: MAIL FROM:<>
Out: 250 2.1.0 Ok
In: RCPT TO:<firstname.lastname@example.org>
Out: 451 4.3.0 <email@example.com>: Temporary lookup failure
Out: 250 2.0.0 Ok
Out: 221 2.0.0 Bye
is the reply-to address and it exists. So what exactly is this error message telling me?