Which destination port or ports should you open?

You are the Office 365 administrator for a company. You plan to use Skype for Business Online on all mobile
devices. Employees currently use the following device types:Android
iOS
Nokia Symbian
Windows Phone
Some users report that they do not receive push notifications. Skype for Business Online must be able to send
push notifications to all devices.
You need to open the required ports in the firewall.
Which destination port or ports should you open?

A.
TCP 443

B.
UDP 3478

C.
TCP/UDP 50,000-59999

D.
TCP 5223

Explanation:
Skype for Business mobile push notifications uses TCP port 5223.