Open ports in the Linux firewall to access POP and IMAP mail servers
To access services such as POP and IMAP mail servers, you’ll need to open certain ports to allow the services through the firewall. There are a few standard ports that are used to access most services. For example, accessing a website generally uses port 80 for normal (HTTP) web pages and port 443 for secure (HTTPS) pages.
* Though SMTP generally uses port 25 for connections, port 587 is actually the preferred port for outbound SMTP traffic due to the widespread abuse of port 25.
Edit iptables rules
Following from the Cloud Server setup, we need to edit the iptables.test.rules files to allow access to those ports. We will use port 25 for SMTP at the moment. You can change it as you see fit.
Open the test rules file using the following command:
sudo nano /etc/iptables.test.rules
Just before the HTTP and HTTPS entries, add the following details:
# Allows SMTP access -A INPUT -p tcp --dport 25 -j ACCEPT # Allows pop and pops connections -A INPUT -p tcp --dport 110 -j ACCEPT -A INPUT -p tcp --dport 995 -j ACCEPT # Allows imap and imaps connections -A INPUT -p tcp --dport 143 -j ACCEPT -A INPUT -p tcp --dport 993 -j ACCEPT
Apply the new rules using the following command:
sudo iptables-restore < /etc/iptables.test.rules
Now check that the rules have been applied using the following command:
sudo iptables -L
This information should be in the output from the command:
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT tcp -- anywhere anywhere tcp dpt:smtp ACCEPT tcp -- anywhere anywhere tcp dpt:pop3 ACCEPT tcp -- anywhere anywhere tcp dpt:pop3s ACCEPT tcp -- anywhere anywhere tcp dpt:imap2 ACCEPT tcp -- anywhere anywhere tcp dpt:imaps
Now we have tested the rules, we need to have them applied on a permanent basis. You will need to have full root access for the next command so use this command in order to enter the root shell:
Now use the following command:
iptables-save > /etc/iptables.up.rules
Now that you have saved the new iptables rules, you can exit the root shell by typing the following command:
Continue the conversation in the Rackspace Community.
©2016 Rackspace US, Inc.
Except where otherwise noted, content on this site is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License