Hello

 

We've just launched postfix with Mailscanner and spamassasin on our mail
server.

 

Everything is working great, but we've encountered very funny and strange
problem.

 

We've recieved an email which was classified as spamm by it's sender IP
address by RBL list.

 

Additionally sender address didn't pass DMARC verification and had RUF email
in it's DNS record.

 

Our mail system based on DMARC DNS record send a DMARC report to that email.

 

However email in that record was invalid, and the destination server bounced
it with reason that the user is unknown. 

 

This bounced email was sent to us and was also classified as SPAM and was
rejected + again didn't pass DMARC verification which resulted in another
email with report to the invalid email adress which is in RUF DNS record. 

 

You see the point? We got stuck in a loop of sending DMARC reports which are
beeing bounced because of unknown user.

 

Is there any way to prevent such situations?

 

Right now we simply blocked that IP address on mail server firewall but this
could happen any time again in the future.

 

Anyone every encountered this kind of situation?

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