I'm trying to figure out how to integrate Vanilla with Mandrill without using SMTP. My current host doesn't allow sending mail via external SMTP, and they throttle outgoing emails to 125/hour. I currently have 62 users of my forum, and if I turn on EmailSubscribe, well, you do the math and you'll see the problem.
Mandrill has an application API, however.
So I don't know where to start. Do I hack the Vanilla class.email.php so that it uses the Mandrill API instead of sendmail? Should I try writing a plugin? Should I hack the EmailSubscribe plugin to give it hooks to the Mandrill API?