Lync meeting or Lync conferencing is what many organizations would like to deploy to allow them save money. But companies are now giving up for various reasons, one of which is that they cannot join external meetings (non-federated company meetings). The Microsoft support team will tell you to open Lync federation for this to work or use the Lync web app instead. How do you expect corporate users to be copying meeting URLs and pasting them into web browser and then insert "?SL=1" at the end of the link?
Here is the eror message we get each time we click on join online meeting link in outlook to join a non-federated user's meeting.
For Lync 2010:
"an error has occurred during online meeting"
For Lync 2013:
"An error occured during the Lync Meeting"
Brief description of our network environment:
Our organization deployed a proxy auto-config file for all users as they access the Internet, firewalls and are doing inpections on all traffic. We do not open Lync federation because our Corporate Security Group declined all requests to do so. After many years of struggling, we resolved this issue without opening federation.
On a user's computer, using Lync 2010, open regedit and navigate to
Locate "DisableHttpConnect" and change the value of the REG_DWORD to 0.
By default it is set to 1. Use this new setting to enable the Lync client to fall back to HTTP while connecting to an external meeting as it finds it way around the barricades of firewalls and proxies in your internal network.
For Lync 2013:
And set the value of "DisableHttpConnect" to 0.
After testing, you can create a group policy to set the value to 0 for users.
Finally, ask the user to sign out of Lync and Outlook after you change the value. Then re-open Lync and Outlook again and join the same Non-Federated user meeting.