By the sounds of it you're looking for a free open source solution, but if you've got a bit of a budget I'd recommend Email Newsletter Software for Web Designers - Campaign Monitor

Used it today to send out a mailer to 400 people and am very impressed with it. They charge per campaign you send out, costs 5 dollars + 1 cent for every recipient, so today it cost 9 dollars.

You get a report on deliveries, who forwarded the email to friends (and to who), it handles auto-removal of bounced addresses, unsubscribing, new subscriptions and other very nice little features.

Lots of customisation options. It's pitched at web designers/developers like us so you can create multiple accounts for your various clients, each with any number of lists and campaigns. As well as a personalised login area for each of them where they can view reports.

I played around with PHPList earlier in the week but didn't like the complexity of the interface. Wanted something quick and simple and Campaign Monitor is just that.

Definitely worth a look imo.

PS - I am in no way affialited with Campaign Monitor! ;-)