Hemkrish,
With the first request, that can be done, but you would need know the ip address of the gmail server, then create an ipv4 rule under the firewall tab going from lan to wan. You would first create an allow for that ip range to the gmail server(s), then deny the rest to that range to the server(s).
As for the second part, it would be the same thing. Select the protocol and repeat the above steps.
