Name
MailboxCount — Checks mailbox message count
Retrieves the number of messages for the specified voice
      mailbox.
Example
          Action: MailboxCount
Mailbox: 100@lab 
ActionID: 54321abcde        
          Response: Success
ActionID: 54321abcde
Message: Mailbox Message Count
Mailbox: 100@lab
NewMessages: 2
OldMessages: 0