A company deploys an Office 365 tenant. All employees use Lync Online.
You need to configure the network firewall to support Lync Online. Which ports must you open? To answer, drag the appropriate port number to the correct feature
or features. Each port number may be used once, more than once, or not at all. You may need to drag the split bar between panes or scroll to view content.
Answer: 
Explanation:
Port Protocol Client Usage Direction
443 TLS/PSOM Data Sharing Sessions Outbound
443 STUN/TCP Audio, Video and Application sharing sessions Outbound
3478 STUN/UDP Audio and Video Sessions Outbound
5223 TCP Lync Mobile push notifications Outbound
50000 TO 50039 INCLUSIVE RTC/UDP Audio and Video Sessions Outbound