Linux: Iptables # 14 How to allow POP3 server/protocol request

Posted by Vivek Gite [Last updated: December 28, 2006]

Local e-mail clients use the Post Office Protocol version 3 (POP3) to retrieve e-mail from a remote server over a TCP/IP connection.

POP3 allows to retrieve mail. It uses the TCP port 110. Following two iptable rules allows incoming POP3 request on port 110 for server IP address 202.54.1.20 (open port 110):

You need to add following rule set to your iptables shell script:

iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 202.54.1.20 --dport 110 -m state --state NEW,ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 110 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

In order to block port 110 simply use target REJECT instead of ACCEPT in above rules i.e.:

iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 202.54.1.20 --dport 110 -m state --state NEW,ESTABLISHED -j REJECT

iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 110 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j REJECT

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Discussion on This Article:

Anonymous Says: April 24th, 2006 at 12:49 pm
after runing this “iptables -A INPUT -p tcp -s 0/0 –sport 1024:65535 -d 202.54.1.20 –dport 110 -m state –state NEW,ESTABLISHED -j ACCEPT” It says Device or resource busy. Hint: insmod error can be caused byincorrect module parameters, including invalid IO or IRQ parameters.
what should i do??
Ash Says: December 28th, 2006 at 5:25 pm
-Following two iptable rules allows incoming POP3 request on port 25
+Following two iptable rules allows incoming POP3 request on port 110
nixcraft Says: December 28th, 2006 at 6:03 pm
Ash,

Thanks for heads up.