drop all out going SMTP connection bar two

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Hi,

I would like to drop all out going SMTP connections through our router except smtp1.internal and smtp2.internal on all of the outbound interfaces. I would like to filter on the destination port 25.

Would this be easy to do?

Thanks for any advise,
S.
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Simon Loewen :

Try this:

iptables -t filter -A FORWARD -j ACCEPT -p tcp -d ip.of.smtp1 --dport 25 iptables -t filter -A FORWARD -j ACCEPT -p tcp -d ip.of.smtp2 --dport 25 iptables -t filter -A FORWARD -j DROP -p tcp --dport 25

In our network I have redirected all smtp traffic to our internal SMTP server and then allowed that server to send e-mails... :)