reliable way to send emails (web development)

I'm working on a site that allows users to signup up. I'm currently using php to send activation links to users who sign up. It's just that I've notice开发者_如何学编程d the email doesn't always arrive on time and sometimes, it doesn't even arrive at all. I'd much rather use PHP but with this issue, I can't.

Anyone have some suggestions on alternatives that can also interact with PHP?

---

Take a look at PHP Class: MIME E-mail message sending. It's pretty well documented and ranks 1st on phpclasses.org