Hi Levi,
We use Lotus Notes here, but have elected to support SMTP to send emails as this keeps things clean and means any client should be able to receive it.
In your example, I believe you can also use IT.Helpdesk@CPB.??????, assuming CPB is your domain. Look in your Domino Direcory and find out your default domain and what is specified use after the @. You can additionally specify a specific SMTP email address.
Graham