This only apply after you have installed : TLS/SASL/SSL !
I am using “Virtualmin” so locate your roundcube in here:
/home/[username]/public_html/webmail/config/config.inc.php
Locate this configuration: $config[‘smtp_server’] = ‘localhost’;
Easy fix here!
Remove ‘localhost‘: $config[‘smtp_server’] = ‘ ‘;
Now roundcube will use PHP instead of SMTP
Enjoy!