Please help about smtp proxy issue

[alinagra]

Hi, buddies,
I am using Mantis 1.2.1, the latest stable version. I have setup the LAMP enviroment on Ubuntu server and installed Mantis correctly.
Right now I have a question to send email by SMTP like this:

Our Ubuntu server is located in the internal LAN, and it use http proxy to access the external Internet. Our mail server is the external Internet Web Server.

Ubuntu Server -----> http Proxy --------->Internet Mail Server

So how can I setup the http proxy of Mantis to send SMTP mail? Please help, Thanks a lot in advance!!

Here is my mail configuration:

$g_phpMailer_method = PHPMAILER_METHOD_SMTP; #PHPMAILER_METHOD_MAIL; # or PHPMAILER_METHOD_SMTP, PHPMAILER_METHOD_SENDMAIL
$g_smtp_host = 'smtp.xxx.com'; # used with PHPMAILER_METHOD_SMTP
$g_smtp_username = 'mantis@xxx.com'; # used with PHPMAILER_METHOD_SMTP
$g_smtp_password = 'xxxx'; # used with PHPMAILER_METHOD_SMTP
$g_administrator_email = 'mantis at xxx.com';
$g_webmaster_email = 'mantis at xxx.com';
$g_from_name = 'Mantis Bug Tracker';
$g_from_email = 'mantis at xxx.com'; # the "From: " field in emails
$g_return_path_email = 'mantis at xxx.com'; # the return address for bounced mail
$g_email_receive_own = OFF;
$g_email_send_using_cronjob = OFF;