Using iptables to block for specific services

Question

I am using ipset in conjunction with iptables to create a list of IPs I want to block. I did this:

ipset -N blocking iphash
ipset -A blocking 124.205.11.230
// and repeated this line for all IPs I want to add to "blocking" list

now I have to add this rule to iptables

if I do this

iptables -A INPUT -m set --set blocking src -j DROP

the IPs will be blocked for everything SSH, FTP, etc. I want just to block them from using my email system dovecot, exim.

how do I do that?

Answer 1

iptables -A INPUT -p tcp --dport 25 -m set --set blocking src -j DROP
iptables -A INPUT -p tcp --dport 143 -m set --set blocking src -j DROP

... or whatever ports you're using.