Hello,

We have a co-existence infra of 2010 and 2007 servers. Recently we were decommissioning the 2007 Public Folder after moving all the replicas to 2010 servers.

Decommission is completed.

Now Test-MapiConnectivity command is failing on all 2010 public folder databases.

Error: Failure:

[Microsoft.Exchange.Data.Storage.MailboxUnavailableException]: Cannot open mailbox /o=Exchange DN Path/cn=Microsoft System Attendant. Inner error [Microsoft.Mapi.MapiExceptionUnknownUser]: MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003)

It is still trying to use 2007 System Attendant account to test the mapi connectivity.

Any Idea how we can fix this issue??

How to configure public folder database to use different account for tes

Does this help?

https://social.technet.microsoft.com/Forums/office/en-US/cfe3d3c6-b8df-45e5-aaea-d01041e07312/cannot-open-mailbox-ofirst-organizationouexchange-administrative-group?forum=exchangesvradm