Lync/Skype for Business users will need to have Open Federation set or add ‘dial.vc’ into their allowed Lync/Skype for Business domains list.

In order to search external company or dial.vc domain in Skype for Business, you may also need to put public DNS server addresses like Google IP: 8.8.8.8 and 8.8.4.4 in your DNS server Forwarders.

In China, you may need to put China public DNS IP: 114.114.114.114 and 210.51.176.71