Spam mail how to get rid?

[gatonegro]

Currently a quite large number of returned e-mail keep coming into our Postmaster's Inbox. We receive this kind of message almost every 10 to 15 minutes. It seems that a spammer keeps using e-mail addresses that have our domain but never exist

 

[georgeks]

What do you mean? He sends mail to your domain to users that dont exist and the notifications come to your postmaster inbox or he sends out mail(spam) as if he was a legit domain user, which then returns to you as NDR?

 

[gatonegro]

Sends mail to non-existent users, then we get notifications via the postmaster inbox, we get this almost every ten minutes.