Error: Server replied: 110 Can’t open SMTP stream

Login to the server via shell

edit the file /usr/local/cpanel/base/3rdparty/squirrelmail/config/config.php and change

$useSendmail = false;

to:

$useSendmail = true;

Save and exit this file.

This will correct the error and you will be able to send emails from Squirrlemail