When you register users, have an option to create an archive DB linked to the mailfile.
I'm in the middle of a migration of 500 users from Exchange. I can register the users via a text file but not create an archive DB for each one of them. This archive will in this case be used as target for their migrated Outlook data. Even with scripting this is difficult because you need to handle the archive profile etc...
I have tested an IBM idea : send a mail to all of those users, create an archiving policy to archive documents not modified in 1 day, launch a compact -a the next day .... very long and it doesn't work ! You have to open the mailfile and open the archive settings before it applies. Unacceptable, no?