So I couldn't figure out any way of doing this, and I can't stand stuff like this beating me so I've been messing about with it for the last hour and it's finally working so I thought I'd share what I've done. Maybe this will get spidered, but mostly it'll be here for my future reference!
The long and short of this situation is that OSX includes sendmail, but it seems to be some sort of alias for postfix, so you should actually be configuring postfix. Right now, I should probably clear up that I'm by no means an expert on any of this and it's all been trial and error for me so far so if it doesn't work for you, I can try and help but I can't promise anything.<!--more-->
There are 4 files I used for the following:
MAILSERVER=-YES-then sudo nano -w /etc/postfix/main.cf, find the myhostname variable (by default it's host.domain.tld), uncomment it and change it to your domain (if you're on a machine that doesn't have a DNS, you can make it a domain that you're responsible for so that it doesn't get shut down at the receiving end, but please don't make it google.com or something like that!)
now, open php.ini and look for the sendmail_path variable, uncomment it, make its value sendmail -t -i, save then restart apache. I'm not really sure if this is 100% necessary as there's a comment above that says this is the default value anyway, but it can't hurt!
now open a terminal window and execute the next couple of commands:
% sudo postfix start % tail -f /var/log/mail.logfinally, create a file called mail.php (or whatever!) and add the following to it:
<?php mail( '[email protected]', // your email address 'Test', // email subject 'This is an email', // email body "From: Me <[email protected]>rn" // additional headers ); ?>obviously replace [email protected] with your email address and [email protected] with a valid email address (domain at least, as some mail servers will bounce your email if the sender's domain isn't real). Now navigate to your mail.php file (likely http://localhost/mail.php) and watch your terminal window to see that it's been sent successfully. If it hasn't, let me know if you fixed it and I'll update this - it's annoying to me that there isn't really an answer to this question that I can find so the more comprehensive this is, the more helpful!.
Useful bit, added by Terry Thorne in the comments:
I just thought I’d add for those looking to do this who find that their ISP blocks port 25 you have to route through their server. On Snow Leopard edit /etc/postfix/master.cf and add at the end: mydomain = yourisp.net myorigin = $mydomain relayhost = mail.yourisp.net Obviously replacing yourisp.net with the domain of your ISP (usually the suffix of your email address) and the mail.yourisp.net with your ISP’s smtp server addresss Taken from: http://www.mail-abuse.com/an_rteoutgoing.html