PHP on OS X using external mail server?

I'm trying to get PHP on a Mac OS X server to use an external mail server. It seems that OS X is configured out of the box to use a local copy of sendmail to route mail. We will not be running sendmail on our OS X server and need to tell PHP to use an external SMTP server. I put a php.ini file in /usr/local/lib, and modified the SMTP line to point to our external SMTP server. It still doesn't work. If I run sendmail on the server, it works fine. Any ideas? Thanks, John --