Red Hat Enterprise Linux 6 and its derivative CentOS 6 includes a graphical tool called Firewall Configuration for configuring the firewall options. This article describes how to use the Firewall Configuration tool to open up the ports necessary for providing an email server.

Firewall Configuration (GUI)

This section describes how to use the Firewall Configuration tool to configure the firewall.

Firewall Configuration Startup1. Click System, select Administration and click Firewall. This will launch the Firewall Configuration window.
Firewall2. Click Close in the Firewall Configuration Startup window.
Firewall Authenticate3. Type in the root password and click Authenticate.
NoteIf the Firewall Configuration Startup window does not disappear after clicking Close, click the window behind it to bring the Authenticate window into the foreground.
Firewall Configuration4. In the service list, check Mail (SMTP) and WWW (HTTP).
Firewall Configuration - Other Ports5. Click Other Ports and click Add.
Firewall Configuration - Other Ports - Add6. Select 110 tcp pop3 and click Ok. Do the same for 143 tcp imap.
Firewall Configuration - Other Ports7. Finally, click Apply to save your changes.

Firewall Configuration (TUI)

This section describes how to use the Firewall Configuration text user interface (TUI) tool to configure the firewall.

Firewall Configuration1. Launch the Firewall Configuration tool using the command below.
system-config-firewall-tui
Firewall Configuration2. In Firewall Configuration screen, press the Customize button.
Firewall Configuration3. In the service list, check Mail (SMTP) and WWW (HTTP). Press Forward when you are done.
Firewall Configuration4. Press Add to add a custom port.
Firewall Configuration5. Type in 110 to the field Port and tcp to the field Protocol. Press OK when you are done. Do the same for 143:tcp.
Firewall Configuration6. After adding the two ports press Close.
Firewall Configuration7. Finally, press OK and press Yes to confirm overriding of firewall configuration.
 
NoteYou can see the list of service and port numbers using the command below.
getent services
 

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Posted on 7/31/2011 and last updated on 7/31/2011
Filed under CentOS 6 , Red Hat Enterprise Linux 6 , System Administration