Forgot what the available parameters are on a cmdlet in powershell for exchange

Just use tab completion! Type:

Set-Mailbox -<tab>

When you type a hyphen (-) and then press the TAB key, you cycle through all the available parameters on the cmdlet. Want to narrow your search? Type part
of the parameter’s name and then press the TAB key. Type:

Set-Mailbox -Prohibit<tab>