Exchange System Mailboxes in Individual Message Stores

My question is this:

   When using Exchange 2000 Enterprise, you can setup individual messages stores within
   a Message Store Group. If for the Exchange Server you also have an SMTP connection
   set up for internet, when you create a new Message Store there are 2 entries that are
   created, SMTP (server- ........same number) and SYSTEMMAILBOX (server-...... same number)
   and when I look in AD I see that the SYSTEMMAILBOX has been disabled.

   I presume that is because there is no AD account to match to this new mailbox entry...

  I also guess that the SMTP (server-..... number) is the SMTP Vitual Queue for that specific
  mail store. What is the SYSTEMMAILBOX and the numbers that accompany the entry, these
  look like mail messages and message sizes ?

  What happens if you delete the diabled SYSTEMMALBOX account in active directory?

  Regards


  Colin