Using iptables to block for specific services

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http://unix.stackexchange.com – 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 // 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? (HowTos)