The configuration that supports these is still used by most clients but was the only available method supported in legacy clients like Lync 2010 and devices like Lync Phone Edition. Not all of the natively interoperable voice and video solutions supported with Lync and Skype for Business today leverage the newer Lyncdiscover web service model and may still need to automatically discover the SIP registrar directly. To do this one must know the proper FQDN of the desired Microsoft SIP registrar. This can be used as a reference for other articles on this site as a common step performed when troubleshooting device registrations to Skype for Business is to manually configure the endpoint. (This content was originally to be part of another article but was split into a separate post for easier reference.) This brief article walks through some common steps which can be used to locate the Fully Qualified Domain Name (FQDN) of a Lync or Skype for Business registrar from either on-premises or online environments.

How to sign up for skype for business