problem sending email with mail()

I am new to this forum and relatively new to php. I wrote an application and I want to be able to send emails from within. The app is running on a Windows 2003 server with SMTP service installed. When I create the email message and send it, it just sits in the queue folder. The mail() function is not returning an error. I am not very familiar with SMTP but i do know the service is running, I set the relay restriction to allow the server to relay through the VS. PHP.ini is set correctly with SMTP = localhost and SMTP_Port=25.

Does anyone have any ideas what can be causing this?

Thanks in advance

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