Microsoft Exchange and Blackberry Server Specialists

Find Hidden Mailboxes

A common problem with migrations is hidden mailboxes. These are mailboxes that haven't been used. As they haven't been used, they will not appear in ESM and are overlooked. However Exchange knows they are there and will stop the uninstall of Exchange 2003 until the accounts are either mail disabled or the mailbox (even though it hasn't been created) has been moved to another server.

To find any outstanding mailboxes you can use "Active Directory Users and Computers".

  1. Start ADUC on the Exchange server.
  2. Right click on your domain at the top and choose "Find".
  3. Click on the "Advanced" tab.
  4. Under "Field", select User, then "Exchange Home Server".
  5. Change the "Condition" from "Starts With" to "Ends With".
  6. In the "Value" field, type in the old Exchange server name and then click add to set the value.
  7. Click find to start a search.

The results will be displayed below the search fields. You can right click on each result and choose from a list of items, which will include "Exchange Tasks" if you are using ADUC on an Exchange server or a machine with the Exchange tools installed. You can then either move the mailboxes, remove the Exchange attributes or even delete the mailbox as required. Once complete the uninstall should proceed as normal.

If the mailbox is empty, for example a service account or similar, then it will probably cause less problems to remove the Exchange attributes and then recreate the mailbox on the new server.

Another method to find the mailboxes is to use dsquery:

Where example.local is your WINDOWS domain, First Admin Group is your Exchange administration group and EXCHSERVER is the name of the Exchange server that you are looking for mailboxes on.

If the uninstall continues to fail, then it may be the "System Attendant" mailbox that is causing the problem. This is an unusual cause in most cases, therefore this procedure should only be followed if nothing else works - it should not be the first thing that is tried. Often people suspect the system mailboxes because they can see those in ESM, whereas the system mailboxes rarely stop the uninstall process because they are supposed to be there. 

Remember: there is no undo tool in ADSIEDIT, so unless you are sure about what you are doing, do not attempt this procedure. One false move can wreck your active directory. Sembee Ltd cannot be held responsible for any data or financial loss incurred by failure of this process to work.

  1. Launch the ADSIEdit tool - start, run and type ADSIEDIT.msc
  2. Open the following location: "Configuration", "CN=Configuration", "CN=Services", "CN=Microsoft Exchange", CN=<Your Exchange Organisation Name>, "CN=Administrative Groups", CN=<your admin group>, CN=Servers, CN=<your server>
  3. In the right hand column, right click on "CN=Microsoft System Attendant" and choose properties.
  4. Find the "homeMTA" entry and double click. Clear the "Value:" Repeat with the "homeMDB"
  5. Close the ADSIedit tool
  6. Wait for your domain controllers to replicate this change or force replication.
  7. In ESM, go to Servers, <your server>, Storage groups, <your storage group>, Mailbox Store.
    Right click on "Mailboxes" and choose "Run Cleanup Agent".
  8. The System Attendant mailbox should now have a red cross over it, allowing you to purge it from the system.

This process should only be followed if you are removing the server totally.