MTA error "Logon Error -2147221219 The Microsoft Exchange Server computer is not available." (51597)

The Mail Target Agent (MTA) log contains the error:

"CSession::Logon Error -2147221219 The Microsoft Exchange Server computer is not available. Either there are network problems or the Microsoft Exchange Server computer is down for maintenance. - MAPI_E_FAILONEPROVIDER (Microsoft Exchange Server Information Store) Low level error: 0x0 File: 'aeWrapHelpers.h' Line '279' "

The target Exchange 2007 server does not have a Public Folder store as required.

Please create a Public Folder store in the Target Exchange 2007 organization:

1. Launch the Exchange Management Console
2. Expand the Server Configuration node, then select the Mailbox node and select the server you want to create the PF store on.
3. Under the Database Management tab, select the storage group that you want to contain the public folder database.
4. In the Actions pane, click New Public Folder Database. Give the database a name and a path, then click New. 

Once the database has been created, stop and restart the MSExchangeIS service.

Please also see solution SOL44851 for information on the requirement for the Public Folder stores in Exchange 2007:

"Migration to Exchange 2007 - what is the requirement regarding Public Folders?"
https://support.quest.com/SUPPORT/index?page=solution&id=SOL44851