One of the selling features of Lync 2010 is the ability to communicate with users outside your organization – be it a remote user, federated or PIC. How can we communicate with a company who has Office 365 subscription?
Lync 2010 doesn’t allow communication with Lync Online (Office 365) out of the box. You need to add a provider for Lync Online for the communication to work. Let me explain.
I have an Office 365 subscription with a Lync user Rajith@uclab.me. My on-premise Lync has an account Chakka@exchangemaster.me. I want my on-premise Lync deployment to communicate with Office 365. How can I do it?
Launch Lync Control Panel and navigate to External User Access –> Provider. There are only three provders by default.
We need to create a new provider for Lync Online. Hit the New button and create a new Hosted Provider. Give LyncOnline as the name of the provider and sipfed.online.lync.com as the access edge fqdn. Select Allow all communications with this provider, unless you want something granular. Hit the Commit button.
Make sure that the new provider is enabled.
That’s it. If you are into PowerShell, open up Lync Shell and run the following command to achieve the same result.
New-CSHostingProvider –identity LyncOnline –ProxyFqdn sipfed.online.lync.com –Enabled $True
You should now be able to add the Office 365 user in your on-premise Lync client and the presence will be updated immediately & you can chat straightaway (provided that you have enabled external communications, covered here).
Sure enough, the Office 365 side (OWA and Lync client) picks up the on-premise presence as well.
Pretty good 
