Exchange Special Mailboxes - System Attendant mailbox

This post is a follow-on post to the SystemMailbox post from last week. Here I’m talking about System Attendant mailbox in Exchange 200x.



System Attendant mailbox

What is it and what is it used for?



Each Exchange 200x server has one (and hopefully only one) System Attendant mailbox. If the server has a System Attendent mailbox (note the misspelling), someone has probably been messing around with the server. Yes, I put that in mostly so it would be indexed with the incorrect spelling as a keyword also. J



The System Attendant mailbox has a folder within it called SpecialPrivateFolderForFreeBusyStorage. This folder is used when CDO or OWA push Free/Busy information up to the store through the MSExchangeFBPublish process.



System Attendant mailbox is also required to be available during mailbox moves. For instance, if you have the mailbox store containing the System Attendant mailbox dismounted during a mailbox move, the move will fail and you’ll find events 9175, 9167, and 1008 in your application event log (see KB.264413).



The SA mailbox is also used to send and receive the messages used by the legacy link monitoring service.



Where can it be found?



There are two parts to make up the complete System Attendant mailbox: a directory object and a mailbox object. The directory object is the actual System Attendant object in the configuration container (ie, at a location like: CN=Microsoft System Attendant,CN=<servername>,CN=Servers,CN=<sitename>,CN=Administrative Groups,CN=<orgname>,CN=Microsoft Exchange,CN=Services,CN=Configuration,CN=<domain> ). This directory object hosts all of the directory attributes associated with the system attendant. There is also a mailbox object, stored in the first Mailbox store created on an Exchange 200x server. This is generally the “Mailbox Store (servername)” store.



When does it get created? Can it be moved and/or recreated?



The System Attendant mailbox is created when the System Attendant is created on a server. It is associated with the first mailbox store created on a server.



If an attempt is made to delete the mailbox store containing the System Attendant mailbox, the following warning will appear:



“Deleting this mailbox store may result in the loss of system messages used by Exchange, such as Free/Busy or Key Management Security. If you choose to continue, you need to restart the system attendant service after the store is deleted.”



If the store is then deleted, the System Attendant mailbox will be moved automatically into another mailbox store on the server (ie – the HomeMDB value on the directory object will be updated). System Attendant service will have to be restarted to reconfigure MSExchangeFBPublish to use the new mailbox location, and the mailbox object may not reappear under the “Mailboxes” node of ESM until it is used in the future.



If there is a System Attendant directory object but no mailbox object (ie – one good cause of this is dropping in a blank store for troubleshooting), the mailbox store object will be recreated automatically in the mailbox store referenced by the HomeMDB attribute as soon as it’s needed.



How can I log onto the System Attendant mailbox?



It can be done, but it’s a fairly complicated set of steps and you’ll have to call PSS to get them.



SHOULD I log on to the System Attendant mailbox?



Probably not. I can’t think of any good reasons for accessing this mailbox without PSS directing you to do so.



What happens if I don’t have a proper System Attendant mailbox?



If there’s no System Attendant mailbox available on a server (and in a mounted and functional mailbox store), anything that requires it will almost certainly fail. You’ll see 9175 events logged in the application log, indicating a failure to logon to this mailbox by the system. You’ll see OWA-generated Free/Busy information not getting updated. You’ll see mailbox moves fail. It’s a very important mailbox to have configured properly and available!



(Added some more on Dec 27, 2004):


Should I delete it? Do I have to delete it before I can uninstall the Exchange server?



Nope, definitely should not delete it. If you’re getting the error “One or more users currently use this mailbox store. These users must be moved to a different mailbox store or be mail disabled before deleting this store. ID no: c1034a7f Exchange System Manager” when trying to remove the mailbox store or uninstall the server, this is not due to the System Attendant Mailbox. Have a look at KB.279202 for more information on how to determine which mailbox is causing this behavior.