Real-Time UC

A Universal Communications Blog by Office Apps and Services MVP Michael LaMontagne

Bugs Lync Skype for Business

Skype for Business anonymous join failure when meeting organizer is disabled for federation

Before we start, I highly recommend you first read Scott Stubberfield’s “Anonymous join from Skype for Business and Lync Clients” blog post:

Now that you understand the anonymous join process, we’ll go into one scenario that I’ve been tracking since Lync Server 2013 RTM (almost 4 years…).
UPDATE Sept 17,2017: Issue resolved, see: Skype for Business Anonymous Join Success When meeting organizer is disabled for federation


  • Company A has Federation Enabled
  • User at Company A has an External Access Policy set to have Federated User Access disabled
  • This User schedules a meeting and sends the invite to an external participant
  • External participant is running the Lync or Skype for Business client
  • External participant tries joining the meeting, but is greeted with “An error occurred during the Skype Meeting”
  • External participant is able to join the meeting if forcing connection via Web App in browser (appends ?sl=1 to the end of the meeting URL)

Let’s compare some client logs for the External participant:

  • Company A Federation Enabled and Meeting organizer Enabled for Federated User Access (Successful federated join):
  • Company A Federation Disabled or External participant’s domain is blocked (Successful anonymous join):
  • Company A Federation Enabled and Meeting organizer Disabled for Federated User Access (Failed anonymous join):

As per Scott’s blog, the following table lists the valid SIP response or diagnostic codes that the client will use to trigger the anonymous join process:

So we have the External participant’s client triggering anonymous join when seeing 504 or 404, but not the 403 response that is received when the meeting organizer is disabled for federation.

Hugo-Octopress Theme | Powered by Hugo