Block all incoming mail traffic except certain addresses

jennyzon · 01-12-2009, 02:30 PM

hi folks,
can you please assist me in using the iptables firewall to block all incoming mail traffic (SMTP port 25) except that of a certain IP(s)? the situation is that we have a server that we only want to receive mail from a particular sender.

thanks,
jenny z.

junpa · 01-13-2009, 06:35 AM

Code:

iptables -A INPUT -m tcp -p tcp --dport 25 -s 1.2.3.4 -j ACCEPT
iptables -A INPUT -m tcp -p tcp --dport 25 -s 1.2.3.5 -j ACCEPT
iptables -A INPUT -m tcp -p tcp --dport 25 -s 1.2.3.6 -j ACCEPT
iptables -A INPUT -m tcp -p tcp --dport 25 -j REJECT

change 1.2.3.x to the ip(s) that you want to allow.

keep in mind that this will append to your already existing
INPUT chain and can be negated by the rules above it.