I can't speak to that. All of my organizations that use it have under 10 users, and I moved them over back when "organizations with fewer than 10 users" were free.

What I can say, though, is that you basically specify the catch-all to go to one user.

So you would have drew@htclyg.com, and mike@htclyg.com. Those are two separate accounts. Drew doesn't see Mike's email, and the opposite is also true. Then you set up the catch-all to go to Drew. Drew will now see any-email-address-here-except-mike@htclyg.com. Mike will only see email to mike@htclyg.com.

Make sense?