Having read through this issue found at
I have the same problem except My System Attendant does NOT have a valid homeMDB and homeMTA and System Attendant doesn't have a mailbox in my mailbox store. Basically I know what happened, a few months ago, we lost our information store and built a new one. I guess the system attendant was on the one we lost. But for some reason, the entries in the ADSI edit tool don't even list the OLD location of homeMDB and homeMTA. that's the weird part.
Is there any easy way to rebuild this mailbox?