Error joining a Lync conference that is organized by a different company

Brian Hadfield -

When attempting to join a Lync meeting that is organized by another company, you are unable to successfully join the conference and receive the following error message:


reference ID 43 (source ID 241)


This is caused by an issue with Lync federation between the meeting organizer's domain and the meeting participant's domain.  This creates a situation where Lync will not allow a participant from a non-federated domain to join a conference as an authenticated user, but because the Lync client is installed on the local machine and the Lync Join Launcher page detects the client is installed it will attempt to join with the full client in-place of the web client.  There is no option to use the Lync 2013 client and join the conference as a guest.

This issue can be resolved by either verifying the Lync federations settings or by having participants join the conference using the Lync 2013 Web App.

Troubleshooting Lync federation issues

If the user is trying to join as an authenticated user from another Lync or OCS organization:

  • Your Lync Online organization must have External Communications enabled, and the external user’s domain must be in the Allow list.

NOTE:  In order to allow for federation with external domains, additional steps are required.  Please see the Configuring Lync Federation article for the requirements.

  • The external organization must have federation configured correctly on their platform.

Joining meetings by using the Lync Web App

If the troubleshooting steps don't resolve the issue or if joining the meeting immediately is a bigger concern, the the Lync Web App.  The Lync 2013 Web App has replaced the Lync Attendee client and now supports audio and video.

NOTE:  For more information on Lync client features, see the What is Lync Web App? article.

  1. Copy the Join URL from the meeting invite, and then paste it into Internet Explorer. (Warning: Don't press Enter yet.)
  2. Add ?sl=1 to the end of the URL, and then press Enter.

    NOTE: You must have Silverlight installed to use the advanced features of the Lync Web App.
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