The Internal Message Delivery Health Test is configured to use an account that has a mailbox hosted on an Exchange 2007 mailbox server. When you run the test against Exchange 2010 servers the test fails with a status of Not Complete
The account that is configured to run the test (the Exchange 2007 mailbox user) cannot successfully logon to the Exchange 2010 mailboxes to send the test email.
Create an Internal Message Delivery Health test to be run only against your Exchange 2010 server and configure the test to use an account that has a mailbox hosted on an Exchange 2010 mailbox server as well as has Full Access rights to each of the Exchange 2010 test mailboxes.
If the test still fails, grant the account running the test Send-As and Receive-As rights to each of the test mailboxes.
Note: We recommend that test mailboxes created for these tests only be used for Spotlight on Messaging.