Add some options: whitelist some external IPs and/or access from LAN

[marclaporte]

You are on premise, and ClearOS is the gateway. ISP stops working, and thus, you can't receive the email. That is a problem.

Also, perhaps your email provider is down. We could add an option that access from the LAN would not require 2FA. And perhaps we should make this a bit more flexible and to whitelist specific IPs.

Thanks Lowell for the suggestion.