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July 24, 2008 12:15pm pdt
 
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How do I block port 25 (SMTP) to all LAN clients except my two mail servers? (CBL blocklist)

Tags: block, port, iptables, 25, smtp
Hello everyone!

Simple question, but I couldn´t find exactly what I needed on the KB:
The LAN has over 70 cpus in workgroup environment. To make things worse, we don´t have any corporate antivirus solution, we just install regular AV´s on each machine and hope for the best. Anyway, my question is:

To keep mass-mailing viruses at bay, and trying not get ourselves listed at CBL, I would like to block smtp traffic from getting out of the network, with the exception of the mail servers of course. Providing internet access, we have a SUSE/Squid/iptables server.

I would like to know what do I have to add to the iptables configuration file to allow smtp access only to two (or more) ip addresses and block all the rest (LAN only).

2 MTA´s (10.0.0.2 and 10.0.0.3)
LAN (10.0.0.50-255 MASK 255.240.0.0)
Linux (10.0.0.5 squid iptables - not transparent)

Tyvm!
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Question Stats
Zone: Networking
Question Asked By: sot010174
Solution Provided By: Blaz
Participating Experts: 1
Solution Grade: A
Views: 21
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Accepted Solution by Blaz:

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