This article describes the fix for the Skype for Business/Lync Attendee error that external contacts receive when they try to connect.

The scenario of the issue:

  1. Skype for Business user initiates a meeting and invites an external contact.
  2. External contact tries to connect via Skype for Business/Lync Attendee, but receives the following error:
    Cannot sign in becasue the server is temporarily unavailable. Reference error ID 28 (source ID 238)
    Cannot sign in the Skype for Business/Lync Attendee because of a problem connecting to the server. Reference error ID 102 (source ID 238)

To fix the connection:

  • Create a SRV record for your domain. For instance, if invites the SRV record should be created for
    You may need to contact your DNS provider to add this record.

Syntax of SRV record:

  • Service: _sip
  • Protocol: _tls
  • Port number: 5061
  • Host: lyncsip.XX.XX.XX. For instance,
    You can find the correct setting in HostPilotĀ® Control Panel > Services > Skype for Business > Instructions.
  • Priority and weight can be left 0.

To verify the record is created successfully and propagated:

  1. Navigate to Start, find Cmd and open it.
  2. Type the following lines one by one and hit ENTER after each:
    Note: If you do not know someDNSserverIP you may use

    nslookup - someDNSserverIP


    set q=SRV
  3. The results should look like this:
     priority = 0
     weight = 0
     port = 5061
     srv hostname = lyncsip.XX.XX.XX