Before today theย sendmail command-line tool was disabled on our servers so all apps and scripts had to connect to our SMTP servers to send an email.
As of today sendmail is enabled on all servers which means that any app or script that uses sendmail to send emails will just work without any modification:

[testweb100@web100 ~]$ sendmail support@webfaction.com
Subject: Help me

Just testing sendmail<ctrl-D>
[testweb100@web100 ~]$
<email was sent>

This also means that the native PHP function mail() now works without any extra code:

[testweb100@web100 ~]$ cat testsendmail.php
<?php
$message = "Just testing sendmailn";
mail('support@webfaction.com', 'Help me', $message);
?>
[testweb100@web100 ~]$ php testsendmail.php
[testweb100@web100 ~]$
<email was sent>

Another place where it can be useful is if you want to receive error emails about failing cronjobs: just add “MAILTO=youremailaddress@yourdomain.com” at the top of your crontab and you’ll start receiving error notifications.

Under the hood the sendmail binary is actually a patched version of msmtp (a sendmail-compatible mail tool) which connects to our SMTP servers to send the email.