Enable core Microsoft Teams calling functionality on compatible legacy SIP phones with SIP Gateway

Hi, to anyone that can be of interest, I post further experience on this matter. After achieving a Ply phone working with Teams SIP gateway, I have checked the required ports in the firewall. The ports and IPs stated in the manual should be opened in the outbound direction. I have deleted all the inbound rules and restarted the phone, and it continues working properly.

Somehow this has sense. The inbound ports should be opened only in case the communication between the gateway and phone is started by the gateway. This would require the phone to have a fixed IP address to allow some NAT rules to be created to route the incoming traffic to the phone. But as we are using DHCP for the phones, this cannot be done. So I supposed that all traffic is always started by the phone in the direction to the gateway, and this one replies. This kind of communication is normal behavior and, as far as I know, this does not require the inbound traffic to be declared explicitly in the firewalls.

Of course, the outbound traffic needs to be allowed in the firewall for the ports and destination IPs stated in the manual.

I am not sure if the explanation is quite clear....