I had installed 1.2.17 and had attempted to configure the email settings using the settings listed below. However they would not work no matter what I tried. I verified that there were no firewall issues and that another sample script was sending email ok using the same connections settings.

$g_allow_signup = ON;
$g_enable_email_notification = ON;
$g_phpMailer_method = PHPMAILER_METHOD_SMTP;
$g_smtp_host = '192.168.1.150';
$g_smtp_port = 2506;
$g_from_email = 'mantis@mydomain.ie';
$g_administrator_email = 'admin@mydomain.ie';
$g_smtp_connection_mode = '';
$g_smtp_username = 'admin@mydomain.ie';
$g_smtp_password = 'password';

I was eventually able to track down the issue. The documentation says that when the smtp connection mode is set as follows "$g_smtp_connection_mode=''", the username and password should be ignored.

However this is not the case, even though the connection mode was set to '', the system kept reporting "SMTP Error: Could not authenticate."

As soon as I removed the username and password variables, the email sent fine.

$g_allow_signup = ON;
$g_enable_email_notification = ON;
$g_phpMailer_method = PHPMAILER_METHOD_SMTP;
$g_smtp_host = '192.168.1.150';
$g_smtp_port = 2506;
$g_from_email = 'mantis@mydomain.ie';
$g_administrator_email = 'admin@mydomain.ie';