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Can you help me with iptables. I want to allow send emails locally on server, and forbid to send anywhere else. i made some changes in iptables, but without success. I have CentOS. Only rule that works

-A OUTPUT -p tcp -m multiport --dport 25,465,587 -j DROP

But it blocks all SMTP traffic. Thank you in advance!

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-A OUTPUT -p tcp -m multiport ! -o lo --dport 25,465,587 -j DROP
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