I’m getting an error on a couple of my servers when trying to send email from webmail.

Connection timed out
Server replied: 110 Can’t open SMTP stream.

Solution :–

I found the config for cpanel’s SM:
/usr/local/cpanel/base/3rdparty/squirrelmail/config/config.php

I just changed:
$useSendmail = false;

to:
$useSendmail = true;

thats all