This is just FYI on a cmdlet which I use daily – Test-MapiConnectivity!
Use Test-MapiConnectivity to troubleshoot connectivity problems. Remember as the name implies, it will only test MAPI connectivity.
Use this to test connectivity between your users and your servers.
Use it in the following format:
Mailboxes: Get-Mailbox <Mailbox Name> | Test-MapiConnectivity
Mailbox databases: Get-MailboxDatabase <Database Name> | Test-MapiConnectivity
Servers: Get-MailboxServer <Server Name> | Test-MapiConnectivity
The above information is available as a tip in EMS.