OK, see you weren't clear on your situation.
- You have records of names and addresses of members.
- You only want members to subscribe to the announcement list.
- You don't have a process in place that can verify an e-mail address belongs to a member.
You would need something like this:
1. Visitors submits e-mail address to a web form.
2. CGI script sends confirmation e-mail to the e-mail address.
3. Recipient visits URL provided in message.
4. URL is to a another web form, where recipient must verify name and address.
5. CGI script sends you a message that lets you know to access the web panel and subscribe the e-mail address to the announce list.
Either that or ask members to call you or write you, etc.
Perl / MySQL / HTML+CSS