It's probably not 100% on-target for what you want to do (not to mention
being overkill, perhaps), but I use Drupal to do exactly what you're
describing, using the Subscriptions add-on module.
Basically, people sign up, read and post to topical forums (web based)
but then also have the option to "subscribe" to any forum (or specific
thread, even) and have new posts to that area emailed to them. Anyway,
thought you might want to peek at it.
http://drupal.org
In article <dh**********@panix3.panix.com>,
ad****@panix.com says...
I'm going to be collecting lots (a few thousand) email addys. Each of
these people will be interested in recieving mail on one or more
topics, with an open ended and growing number of topics. Mailman with
a BD application behing it might be ideal as it would let users add
and delete themselves and each topic would have it's own email list
name identity.
Any suggestions for a PHP/mysql application to do this?>