I've got mine set up so that php uses msmtp to send mail through Google via TLS. I used the following guide to set that up:
http://nanotux.com/blog/the-ultimate-server/4/#l-mail
The only problem I had was that no matter how many times I changed php.ini, php just wouldn't take my sendmail override. The phpinfo() function said that it was using the ini I was editing, but it just wouldn't take. I think I restarted lighttpd a million times.
So finally I just set up a symbolic link where php wanted to use sendmail to point to msmtp. It's none the wiser.
It works well, but it is a little slow. Whenever a user leaves a comment there is a noticeable delay while it connects securely to google and sends the mail.
It's not an unbearable delay, but it's slower than the rest of my site.
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