There is Aweber for example (a hefty...at least for my budget at this time, $19 per month) and MailChimp (with some limitations on the free account).

I want neither.

I can build my own.

In PHP.

Does anyone know of any good guides online to building your own mail handler?

I don't need the fancy web interface and I don't need much of what these two offer. I just need the ability to send out HTML emails on a given schedule to those who have signed up to receive a newsletter. Double opt-in capability. I think that's really about it.

Carlos