I have been struggling with this problem for the last 2 days and finally figured out the solution. Your mileage may vary depending on your network configuration but first some background on mine. I have a Lighttpd web server that i am running some PHP mail scripts on. We are trying to use our company’s MTA to relay messages so i had this line in the sendmail.cf file, with 10.0.0.116 being the IP address of our MTA.
define(`SMART_HOST', `10.0.0.116')dnl
Still, things didn’t seem to want to work. My network administrator wasn’t evening seeing the mail attempts on our mail server so the problem was definitely on the webserver.
Turns out (as these things often are) that it was a dumb syntax problem. The following change fixed everything:
define(`SMART_HOST', `[10.0.0.116]')dnl
Hope this helps if you are having a similar problem.
