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URGENT: Blocking Access to SMTP from the Internet

Hi Friends!

I have an urgent problem:

After having much trouble with spammers after having smtp-relay open to the internet for 1 day, we still get very much attempts of relaying. So i urgently need to know how to block access to port 25 for everyone who tries to access it from the internet. 

thank you!

Robert


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  • Enable the SMTP proxy, and allow only your mail host(s) SMTP relaying priveledges by putting them in the allowed networks field in the outgoing mail section, also turn on verify senders address and use some of the RBL services available.  For internal mailhosts, add a rule to allow SMTP (TCP 25)  to the firewall's interface.