How to prevent spammers sending bogus@mydomain emails out of my name

Question

Lately I receive a lot of Delivery Status Notification (Failure) e-mails.

Bogus spam email is sent from blablaxx@mydomain to other emailadresses, and bounce back to my catch-all info@mydomain with above error-message.

Off course the blablaxx@mydomain email-addresses are non-existing and AFAICS the emails are sent from different foreign ip-addresses.

I've setup a DNS txt SPF record, but that doesn't seem to help much.

What can I do more?

Thx, checking my SPF record I get a error: Too many DNS lookups (count=17) . Does that mean it doesn't work? And how to fix that? — Janghou, Dec 12 '15 at 15:27
Another SPF checking tool Unified eMail SPF Analyzer with more details — Janghou, Dec 12 '15 at 15:34

score 5 · Answer 1 · answered Dec 11 '15 at 10:19

You cannot prevent them. Period.

You can only make it easier for other mailservers to detect those mails as illegitimate by using SPF (as you already do) and DKIM. -- Next problem is: it is very bad practice to bounce back mails to unknown sources. Mailservers like that are not configured with current best practices, so they probably will not filter incoming mail with SPF or DKIM either.

How to prevent spammers sending bogus@mydomain emails out of my name

1 Answers1