You can't do Gmail direct from the machine.
SHA-2 is a requirement for Gmail and Office365 as of January, this model doesn't support it at all, so it is impossible to work with Gmail fully, or directly.
You can send from a gmail account to another gmail hosted account via the APSMX server, but not to any address that is not hosted by gmail ,like AT&T ,Godaddy, yahoo, MSN etc etc. But you would be better off using a relay like SMTP2Go.
I have no idea if it could work for AT&T, I'm not a customer and am outside of the US.