How to add a smtp proxy address to a Exchange 2010 maibox via Powershell

This is a Powershell snippet to add a smtp proxy address to an existing mailbox in a Exchange 2010 environment.
It must run on a machine with installed Exchange 2010 Management Shell.

#Load the Exchange 2010 SnapIns and establish a management session
Add-PSSnapin Microsoft.Exchange.Management.PowerShell.E2010
 . $env:ExchangeInstallPath\bin\RemoteExchange.ps1 | Out-Null
 Connect-ExchangeServer -auto

#Add Exchange Proxy Address to users mailbox
$mbx = get-mailbox "JSmith"
$col_proxyaddr = $mbx.EmailAddresses
$col_proxyaddr.Add("jimbo@domain.com")
set-mailbox "JSmith" -EmailAddresses $col_proxyaddr