Error : 111 Can’t open SMTP stream – SquirrelMail

ERROR:

Message not sent. Server replied:
Connection refused
111 Can’t open SMTP stream. 

Solutions:
> Cpanel version of SquirrelMail does not work.

1) config for Squirrelmail:
/usr/local/cpanel/base/3rdparty/squirrelmail/config/config.php

I just changed:
$useSendmail = false;

to:
$useSendmail = true;
2)Enabling the SMTP tweak:
It is likely related to an iptables rule used to deny connections from those other than exim, mailman and root. Turning the SMTP Tweak on and then off should recreate this rule correctly.
Main >> Security Center >> SMTP Tweak
3) Editing the CSF conf:

# Block outgoing SMTP except for root, exim and mailman (forces scripts/users
# to use the exim/sendmail binary instead of sockets access). This replaces the
# protection as WHM > Tweak Settings > SMTP Tweaks. This will block hosting
# clients from using your server as an SMTP relay

SMTP_BLOCK = 1

# If SMTP_BLOCK is enabled but you want to allow local connections to port 25
# on the server (e.g. for web scripts) then enable this option too
SMTP_ALLOWLOCAL = 1
Out of these three , one will work for sure.