A fresh install of Squirrelmail with SELinux enabled will not allow you to login. You get the following error message:
Error connecting to IMAP server: localhost. 13 : Permission denied
The SELinux boolean "httpd_can_network_connect" must be set. To check its state:
getsebool httpd_can_network_connect
To set it:
setsebool -P httpd_can_network_connect=1