[Mailman-Users] Maximum number of subscribers?

[John Lewis]

I can't remember the specific details, but what is the maximum number of
subscribers that mailman can handle?  What is the practical number?

If it can hold thousands, is there any easy way to search the member list
for specific addresses?

The reason I ask this is I have a 19,000 member list that I'm thinking of
migrating, and some of the addresses in it are not the current addresses
users are using...  So when they ask to be removed, and can't find their
exact address, I need to do the greping to find them.

Also, do all users have to have passwords?  I can disable that can't I?

If these are dumb questions that have been answered somewhere, please point
me in that direction.

Thanks.