iSOblog

i just wanted to send a mail to phoronix, asking them about their linux benchmarking suite.

however, my mail got bounced immediately;

This is the mail system at host mail.pascal-schwarz.ch.

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system: host phoronix.com[209.62.40.52] said: 550-Verification failed for nottheirmail@phoronix.com
550-The mail server could not deliver mail to notmyemail@pascal-schwarz.ch. The account or domain may not exist, they may be blacklisted, or missing the proper dns entries. 550 Sender verify failed (in reply to RCPT TO command)

i was a little surprised and sent my email using another address hosted on the same server, which worked great. so it couldn’t be my mail server being on a black list.

after a little googling, i found this forum thread. the posters problem may be related to exchange (didn’t read the whole thread) but the part

Moreover, some mail server will reject email for domain whose ISP’s MX
record was pointing to an IP address instead of to a DNS name. If this is
your case, you can resolve the issue by changing the MX record to a DNS
name which then resolved to an IP address.

made it clear to me: while my other email address has an mx-entry in the form of mail.domain.invalid, the pascal-schwarz.ch mx entry was the ip of the mail server. after changing this to a dns entry pointing to the same address, the problem was gone.