SquirrelMail by default will contact the IMAP server on the localhost.
Make sure the xinetd daemon is configured to start at boot up. This is shown by the word "on" listed for init levels 3, 4, and 5 as shown below.
# chkconfig --list xinetd
xinetd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
If all levels are shown as "off" then enable xinetd by running this command.
# chkconfig --add xinetd