iis 7.5 email issues

Closed - This job posting has been filled and work has been completed.

Job Description

We have two ecommerce sites that run on php and some specialty pages that run on asp.net
About two months ago, with no apparent reason, the ecommerce sites stopped sending out automated mails (ie upon purchase, etc). However, the asp.net pages continued functioning (sending out emails as designed).
I've looked at the problem and had others look at it and we've been stumped.
I need to get the server back to sending out the ecommerce mails so customers get notification of purchase etc.
Please do not apply if you do not have proficiency in php, iis, and smtp.