I'm using a CentOS 5 virtual machine (from here) as a development server for my website. The problem is that the PHP mail() function can't get emails out to my gmail account, even though the VM has an active internet connection. mail() maps straight through to sendmail, so it's got to be a sendmail configuration issue. Now, I'm pretty comfortable playing around with Linux configuration stuff by now, but sendmail.cf and sendmail.mc are pretty frickin' intimidating and undocumented. Anyone have some quick pointers on how to get mail to work on my development VM without resorting to using an outside SMTP server like gmail? Thanks!

If Sendmail configuration intimidates you (it -- among other things -- certainly does me), you may want to try using another MTA, if possible. Most other MTAs implement a sendmail compatibility interface, if that is what PHP is using. I've had good luck with Courier personally, though Postfix, qmail, and exim are popular.

If that is not possible, is PHP giving you any useful error message as a result of your attempts?