Troubleshooting the user access problems to the mailbox server in Exchange 2013

I have put together a list of quick checks that can be performed on a mailbox server if users are experiencing issues accessing thier mailbox.

Check networking settings (DNS, Default Gateway) on the clients workstation:

Run outlook.exe with the rpcdiag switch:

outlook /rcpdiag

and verify with a network sniffer such as Process Hacker or System Explorer (or netstat) that you can see RPC requests (over TCP Port 443) connected to your exchange server.

Check the mailbox database assosiated with the user is mounted:

Get-Mailbox "user@domain.com" | FL *Database*
Get-MailboxDatabaseCopyStatus -Identity "Database Name"

Ensure there is MAPI connectivity to the mailbox - this can be performed using the Test-MapiConnectivity cmdlet which indirectly checks the Exchange Store / Store Worker, MAPI Server and Directory Service Access:

Test-MapiConnectivity -Identity "user@domain.com"
OR for testing system mailboxes of a specific database we issue:
Test-MapiConnectivity -Database "Database Name"
OR for testing system mailboxes of a specific server we issue:
Test-MapiConnectivity -Server "server-name"

Check the throttling policy applied to the user - specifically the RCA* attributes (RPC Request Limiting):

Get-ThrottlingPolicy | FL *RCA*