Does hosts.deny work against SMTP RCPT brute force attacks

[aceyzeriat]

Hello

I have had trouble with SSH / FTP hackers trying brute force attacks but that was easily solved with Denyhost.

Now I have a more tricky attack,
A hacker trying every combination of mail adresse on one of the domaine I host.
Each attempt comes from a different server

After a while I noticed the servers are indeed cyclic so there is a finite number of servers to ban from connecting to my SMTP.

Is there an easy way to ban a an URL from connecting to my SMTP ?

Thanks,
Arnaud