pf and blocking on smtp

gpatrick · #1 **(View Single Post)** 15th February 2012

I'm using OpenSMTPD for my mail server which is a pleasure compared to Sendmail. At times in my maillog there are attempts made to relay mail from various IPs. Can I add a rule like the one below to stifle any further attempts from that IP? I realize the IPs may and probably will change, but I'd like to add any extra protection I can. I'm currently blocking IPs from N Korea, China, and certain other countries.

Code:

pass quick proto tcp from any to any port 25 \
        flags S/SA keep state \
        (max-src-conn 15, max-src-conn-rate 5/3, \
        overload <bruteforce> flush global)

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