Step 1: Verify the Lyncdiscover CNAME recordTo verify that the Lyncdiscover CNAME record is present in the Domain Name System (DNS) records, go to the Lync Connectivity Analyzer, and select Office 365 Custom/Vanity Domain Name Settings Test for Lync. Enter the sign-in address that you're using when you to try to sign in to Skype for Business Online (for example, firstname.lastname@example.org), and start the test.
If any issues are detected, check the DNS configuration with your domain registrar. For instructions about how to configure DNS for the most common DNS providers, see the following Microsoft Office 365 website:
Step 2: Try a Wi-Fi connectionAfter you verify that the Lyncdiscover CNAME record exists in DNS, check whether a Wi-Fi connection is available. If a Wi-Fi connection is available, try to connect to Skype for Business Online. This test determines whether the DNS lookup failure is occurring on the mobile carrier, the Wi-Fi connection, or both.
Step 3: Query DNS from the mobile carrierThe next step to check whether the mobile device can resolve the Lyncdiscover CNAME record in DNS is to query DNS from the phone itself. This is difficult to do because most mobile devices don't include integrated network diagnostic tools. So, users have to download an application that performs these kinds of functions. Demonstrating the use of these applications is outside the scope of this article and outside the scope of Office 365 technical support. You may need to contact your carrier for additional assistance if the connection is only failing when connected to your data carrier.
- The Lyncdiscover CNAME record isn't set up.
- The Lyncdiscover CNAME record is set up incorrectly.
- The Wi-Fi connection is blocking DNS queries.
- DNS Record Type: CNAME
- Name: Lyncdiscover
- Value/Destination: webdir.online.lync.com