Setting up to sent test emails to another mailer

Hi, I am trying to set up a phplist to send test emails to another server.
I found this in the config
//# test vs blast
// you can send test messages via a different SMTP host than the actual campaign queue
// if not set, these default to the above PHPMAILERHOST and PHPMAILERPORT
// define(‘PHPMAILERTESTHOST’,‘’);
If I set this up does anyone know if this uses:
//$phpmailer_smtpuser = ‘smtpuser’;
//$phpmailer_smtppassword = ‘smtppassword’;
and does the “blast” send still use the original server?
Many thanks.

@Dee999 You may need to look at the phplist code in file admin/class.phplistmailer.php to understand how these settings are used. See the __construct function.