Mailing Service Recommendations?

Am looking at a mail service solution for a prospective client and
need a recommendation.

The client wants to add a service to his existing WordPress
theme that will allow the following:

1. Register new guests with a form onsite
2. Ability for existing members to easily change their email address and update a password
3. Ability for the Administrator to email blast the 500 plus members

Now I know this can be done with Aweber or similar stand-alone company but am looking
for a service or software he can host with a one-time purchase price.

Your suggestions would be appreciated.

Thank you

JQ

You think about getting something custom done using php?

yeah I thought about that but was looking for an off the shelf solution first since it is not real complicated, at least I don't think so.