ERROR: [270-24-45-8004011D] Unable to open target mail store
MAPI error 8004011D
Error: Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance.
Component: Microsoft Exchange Information Store
Low level error: 80040115
- Exchange being over worked
- Exchange is down or not contactable
- Exchange 2010 Client Throttling Policies
- Network Problems
- Running too many Migration machines concurrently
- Running too many threads on the Migration
- Applying too many actions at one time in NME
- Outlook may need to be "reconfigured" to connect to Office 365, Wave 15 if the tenant was recently upgraded.
Check for Firewalls between the migration console and Exchange.
Test connectivity with Outlook to Exchange by launching the Outlook client from the GME migration server.
- Verify there are no Network Problems
- Test with one action with one mailbox
- Change the Client Throttling Policies
If the information above helps try creating a new migration account for each migration machine
For more information on Understanding Client Throttling Policies please review the following TechNet article http://technet.microsoft.com/en-us/library/dd297964.aspx