Building a email communication system

the website i work for is looking to build a email system that can handle a fair few emails (up to a hundred thousand a day).

These comprise emails like registration emails, newsletters, lots of user triggered emails and overnight emails.

At present we queue them in SQL and feed them into an smtp server on one of our web servers when the queue drops below a certain level.

this has caused our mail system to crash as well as hammer our DB server (shared!!!).

We have got an architecture of what we want to build but thought there might be something we could buy off the shelf that allowed us to keep templated emails, lists of recipients, schedule sends etc and report on it. We can't find anything

What do big websites like amazon etc use or people a little smaller but who still send loads of mail (flickr, ebuyer, or other ecommerce sites)