SquirrelMail is an open source standards-based webmail package written in PHP. When installed, SquirrelMail is ready out of the box. All it needs is an installed web server like Apache, SMTP server like Postfix, and IMAP server like Dovecot.

Here are the steps to installing SquirrelMail:

1. Install the EPEL repository package.

2. Install squirrelmail using the command below.
#yum install squirrelmail

3. Start the httpd service.

Configuring SquirrelMail:

1. Launch the SquirrelMail Configuration utility using the command below.
# /usr/share/squirrelmail/config/conf.pl

2 Type in D and press Enter to select the Set pre-defined settings

3 Type in 2 and press Enter to select the Server Settings menu.

4 Type in 1 and press Enter to select the Domain menu. Type in your domain name and press Enter. Save your changes and quit when you are done.

5 Type the commands below to enable SquirrelMail to function properly under SELinux.
#setsebool httpd_can_network_connect on
#setsebool httpd_can_sendmail on