Here is a recent issue I saw....
A customer migrates to Exchange 2010 environment. He replicates his public folders to other 2010 servers. On one or more of the servers he tries to get his mail enabled public folder information by using the get-mailpublicfolder command and specifying the "\publicfolder" parameter.
This will Generate an error code 4 in the application log and generate these details:
(PID 7428, Thread 125)
Task Get-MailPublicFolder writing error when processing record of index 0.
Error: Microsoft.Exchange.Data.Mapi.Common.MapiLogonFailedException: Can't logon to the the Exchange mailbox server 'contoso.com'. No existing 'PublicFolderProxyInformation' matches the following Identity: '\contoso\Test 2'. Make sure that you specified the correct 'PublicFolderProxyInformation' Identity and that you have the necessary permissions to view 'PublicFolderProxyInformation'.. ---> Microsoft.Mapi.MapiExceptionLogonFailed: MapiExceptionLogonFailed: Unable to make connection to the server. (hr=0x80040111, ec=-2147221231)
Lid: 37053 Win32Error: 0x6A6
There is not a mailbox database mounted on the server that has the System Attendant mailbox associated with it. When the \publicfolder parameter is passed we need to access the system attendant to perform a lookup for the folder path. This seems to be visible mainly on stand alone servers as opposed to a DAG node.
Alternatively you can run the get-mailpublicfolder command with the "alias" specified and get results as expected. This is because we can look up the AD object in the MESO folder.