Connection timed out 110 Can’t open SMTP stream.
root@server [~]#vi /usr/local/cpanel/base/3rdparty/squirrelmail/config/config.php
Search for below make it True.
$useSendmail = false;
$useSendmail = true;
set the Attribute as immutable as below :-
root@server [~]#chattr +ai /usr/local/cpanel/base/3rdparty/squirrelmail/config/config.php
That’s It.