After migrating users to O365 the Lync Client 2013 (on-premises) stopped displaying the meeting icon

In a hybrid scenario where you can have different version of Office installed on your machine you may notice a new issue with Lync Client.

In this particular scenario, and I believe only at the company that I'm working we have that. See below:

Win7 and Office 2010 + Lync Client 2013 (we have a Lync 2013!)

In that scenario after moving the Exchange mailbox (on-premises) to a new Exchange Online environment all users cannot see the meeting icon in their Lync Client.

That happens because the EWS cannot contact the properly both environment.


Solution:

• As a workaround changed the default URL to use HTTPS instead:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSOIdentityCRL\Environment\Production]
"RemoteFile"=https://clientconfig.microsoftonline-p.net/PPCRLconfig.srf
• With this key set the calendar icon appears and EWS status shows OK in Lync configuration information

That key already exist in Office2013! :)