Using php’s Sendmail in OS X Server 10.2.8

Hello, I have been searching for a very long time to find a solution to this problem, so any feedback will be greatly appriciated. I have a shopping cart system that uses the php mail() function to send order confirmations to its owner when an order is placed and also an email to the customer. I have not had any problems using this same system on linux bases serves. Can anyone please shed some light on this? Thanks, Ryan