This problem happens because your account is not a member of the “Discovery Management” role. Since your account does not have permission to perform searches, Powershell does not import the Search-Mailbox cmdlet.
Web Server (IIS) role with the follow server role services:
Static Content Compression
Web Server (IIS) Support
IIS 6 Metabase Compatibility
If you already installed .net 4.0 then you will need to run this command to register IIS with .net 4.0
$passphrase = ConvertTo-SecureString -asPlainText -Force Set-SPPassPhrase -PassPhrase $passphrase -Confirm
(Of course, the password immediately after you close the PowerShell I found … 🙂 )