* Accounts : yes, I mean disabling the account vie the proper Admin Request functionality. You might want to arrange for not deleting the mail file, for reference purposes.
* DB security : Lotus has always been very clear on security - a database is secure when it is on the server. Outside the server, all bets are off.
Besides, I have witnessed that there are tools which can destroy the ACL of a Notes db locally. Whatever ACL settings you have, locally they can be undone.
This situation is the same for every single db vendor that exists, with one difference : Notes dbs can be encrypted. Not a sure-fire protection, but it does make things quite a bit more difficult for the casual snooper.
You say "if you get a copy of the mail files" - how would you get it ? Normally, if your Admin is doing a proper job, no user can open any other user's mail db and find anything that is not public (unless there is a delegation in place, but that supposes a level of trust). A copy made in the default, security-enabled scenario, would be a copy of what the user can see (i.e. not much).
In the case of a full copy, the only options to get it are either by gaining physical access to the server (a big no-no in security), or at the very least gaining access to the user's PC which has access to the db (a smaller no-no, but still bad). When physical access is possible, there can be no security if the person is not honest and trustworthy.
If no physical access is possible, and the user "copying" does not have ACL access to the db, then there can be no "getting a copy of" a Notes db. Either you have access to it, or you can't open it, much less copy it.
Pascal.