We decommissioned our last Exchange 2003 server the other day. All seamed well and I thought we were done.
A few days later we had our scheduled downtime to apply patches, and I rebooted all three of our Exchange 2010 servers (for the record we are Exchange 2010 SP1 UR3 v3). Next morning people were getting bounce backs from messages destined to mail enabled public folders. The error in the bounce back was:
#554 5.2.0 STOREDRV.Deliver.Exception:ObjectNotFoundException; Failed to process message due to a permanent exception with message The Active Directory user wasn’t found. ObjectNotFoundException: The Active Directory user wasn’t found. ##
I found this thread and this post. The error (as both posts suggested) boiled down to an empty server container from the decommissioned Exchange 2003 infrastructure. This blog post recommend against cleaning all the old entries, so we were nervous about making the change. Seemed unlikely that a single EMPTY container would be causing such a large issue.
We contacted technical support (without mentioning our findings) and they said the exact same thing as our findings above – to remove the empty servers container. When I asked why this single container is causing the problem, they said “This happens because we assume that if a Servers container exists, there will be a System Attendant object somewhere inside it.” To me, this really does not explain “why”, but it was all they offered. We also asked if the deletion of the servers container would impact any other systems and they said “no”. Our final question was: once deleted, did we need to restart services/servers, and they said “no”.
We backed up AD (system state and the C: drive of the PDC) and deleted the empty servers container, held our breath, and . . . all was good. Mail immediately started flowing to the mail enabled public folders.
I thought I would write this up to supplement the above posts, and to add to our experience. Maybe this will help some one? Leave a comment if this helped!