please check squirrelmail link at http://mail3.g********.com/ , it uses IP 64.187.104.173 i think that is old IP and that is the reason for very frequent error “504 Gateway Time-out”.
I have a support ticket for this issue [JH #FRZ-83080-383].
You don’t need to login for this, just keep on refreshing ‘http://64.187.104.173/squirrelmail/src/login.php’ every few seconds and you will see 504 Gateway Time-out error.