Messagestats Mailbox count does not match Exchange. Why is this? (4211022)

The number of Mailboxes counted by Messagestats does not match the number of mailboxes I have in my organization when using Exchange System Manager, Exchange Management console or Powershell to count the mailboxes. Why is this?

Messagestats counts active mailboxes (initialized) and disconnected mailboxes (both disabled and soft-deleted). If mailboxes are created but not logged into and accessed at least once, Messagestats does not count these mailboxes as active and therefore are not included in the reports.

In addition, MessageStats uses MAPI (not ESM, EMC or Powershell) to count how many mailbox objects exist in each mailbox database. MAPI returns the number of objects in the database regardless of the state they are in, if the object exists in the database it is counted.

The tool MFCMAPI can be used to show the number mailbox objects in each mailbox database.

Please note: Quest Support does not support MFCMAPI and cannot assist with any issue you may encounter using this third party tool. The following steps show how to use MFCMAPI to validate the mailbox counts in MessageStats and are provided for informational purposes only:

1. Run mfcmapi.exe using the MessageStats service account
2. Click OK
3. Click Session | Advanced Logon | Logon only (does not display stores)
4. Click New and follow the wizard to create a new profile for the MessageStats service account
5. Click OK to use the new profile
6. Click MDB | Open other mailboxes | Get mailbox table
7. Enter the name of a mailbox server and click OK
8. A list of all the mailbox objects on this mailbox server is returned. The bottom right of the screen shows the Item count (eg. Items: xx)
9. If there is more than one mailbox server close the Mailbox Table window and follow steps 6-8 for each mailbox server, adding the item count from each server to get the total number of mailboxes for the Organization