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

Issue Summary:

  1. Skype for Business/Lync 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 because 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)


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 for SRV record:

  • Service: _sip
  • Protocol: _tls
  • Port number: 5061
  • Host: or or
    Important: to protect your account information, we cannot publish your Server names in the public Knowledge Base. The correct settings can be found under HostPilotĀ® Control Panel > Services > Domain Name > Click on your domain name > Display DNS records > Show System Records. Read the Knowledge Base article on How To Add SRV Record To Your Domain for more information about SRV record syntax.
  • 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