I have a client site that maintains an e-mail list of enthusiasts for periodic sale mailings, etc. Initially, this was handled by simple form posting to a text file, which was then dumped into an offline MS Access database. The list has grown enough, though, that something more automated is needed. Ideally, the features should include the ability for users to automatically unsubscribe themselves as well as change their e-mail address or other info. Automated deletion of undeliverable addresses would be good, too, though I wonder how such a feature would distinguish between transitory conditions (server down, mailbox full) and permanent ones. The list currently collects snail mail info, too, plus some checkbox "interest categories" so that mailings can be targeted. The data should be secure (don't want the competition sucking down this valuable asset). Oh, and since this company has a limited budget, an inexpensive (if not free) tool would be good. Integrated mailing would be OK, but we have a mass e-mail program that seems to work very well. Any suggestions?