Mapi Spooler

I have installed three computers with NT4 SP6. Two have Outlook 97 and one is
Outlook 98 (Office 97 SR2). There are several user profiles on each machine.
The machines are configured so that users are prompted for their password and
user ID when they open Outlook so they can check their mail regardless of who
is logged on to the network. The problem is that, when one user closes
Outlook, the mapi spooler continues to run in the background for one minute
so that the other users can't log in to their mailbox during that time
because the spooler apparently caches the first user's log on credentials. My
question is: how can one change the amount of time that the mapi spooler
(mapisp32.exe) continues to run in the background after Outlook is closed to
reduce the wait time between different users being able to log on to Outlook.