David, suppose a guy is googling boat stuff, wonders into a DBA thread which seems really interesting to him, and he wants to participate in the discussion, which of the following do you want him to experience:
1. He spends some time writing a post. He is not a DBA member. His post never gets forwarded, becomes pending for a day, deleted. Do you want that to happen to him? The biggest benefit of having an online archive of your mailing list is that new users will find the content in your amazing forum and join you and enlarge your group. If his post gets deleted, of course he will lose, but you lose a potential member too.
2. He sees a notice, telling him only member can post in this forum. He clicks a link to request to become a member. You get the requests and approves him as a member. You add him to the list. Then you click a link to send him a notice that he is already a member. Then he makes a post.
I would choose 2. Because the poor guy doesn't waste time composing a post which may or may not get accepted, and could even get deleted. Plus, you get a chance to grow your membership.
#2 is the new feature that we will have.
As for adding people to the authorized list - it's not like you need to add them one by one. There will be a textbox which you can dump your current subscriber list into it. The email list is actually already in our database, so we could do it on our end too. But it's better to give you the control, so you can decide when to add or remove.