[Rspamd-Users] Return-Path validation

[Gerald Galster]

> Yes, I meant exactly callback verification.
> 
> Have used this technique for a while already, surprised it is considered abusive.
> 
> Thanks for sharing this information, I will reconsider using it.

As you are using postfix:

https://www.postfix.org/ADDRESS_VERIFICATION_README.html

"Some sites may denylist you when you are probing them too often
(a probe is an SMTP session that does not deliver mail), or when
you are probing them too often for a non-existent address. This
is one reason why you should use sender address verification
sparingly, if at all, when your site receives lots of email."

Best regards,
Gerald