With Exchange Server 2010, recently i used the Test-MapiConnectivity cmdlet. Because it verifies server functionality by logging on to the mailbox that you specify. This cmdlet logs on to the mailbox that you specify (or to the SystemMailbox if you don't specify the Identity parameter) and retrieves a list of items in the Inbox. Logging on to the mailbox tests two critical protocols used when a client connects to a Mailbox server: MAPI and LDAP. During authentication, the Test-MapiConnectivity cmdlet indirectly verifies that the MAPI server, Exchange store, and Directory Service Access (DSAccess) are working.

It logs on to the mailbox that you specify using the credentials of the account with which you are logged on to the local computer. After a successful authentication, the Test-MapiConnectivity cmdlet accesses the mailbox to verify that the database is working. If a successful connection to a mailbox is made, the cmdlet also determines the time that the logon attempt occurred.

In order to test the connectivity to the server ‘Serverx’ then it should be used as,
Test-MapiConnectivity -Server "Serverx"

In order to test the connectivity to a mailbox, specified as a domain name (contoso) and user name (user1) then it should be used as,
Test-MapiConnectivity -Identity "contoso\user1"/

Happy troubleshooting!!