Troubleshoot sending out emails in PHP script.

Hello scriptlancers, I have a PHP script and sends out a welcome email when members register. It has stopped sending out emails after I implemented a change. Below is the description of the change I made: Because the script's registration welcome emails sent by my mail server often land in SPAM folder. So I have decided to use smtp service from [login to view URL] and integrate into my server's exim mail agent. I set up AuthSMTP correctly in Exim on my server(my server uses Exim as mail agent you can see more info here [login to view URL]). I'm able to send emails out from my server using Horde, Squirrel, etc. But in the script, welcome emails are NOT sent out anymore after I made the change. I would like the script to be able to send out emails like before. However, I'd like to keep the changes I made. Need your help asap. Must be able to chat. Thanks,