We have a Hybrid Exchange setup with Exchange Online (v15 tenant) and Exchange 2010 on premise.

The hybrid configuration for the most part is working, what I am having an issue with is getting public folders to work for cloud users.

I followed the official documentation here (http://technet.microsoft.com/en-us/library/dn249373(v=exchg.150).aspx) and it kind of works.

When I am accessing Outlook on a public wifi I am able to bring up the cloud mailboxes and on premise public folders show up in Outlook.

When I am accessing email via Outlook as a cloud user on the same LAN as the on premise exchange, the cloud user makes the outlook.com connection for live/ad/archive mailbox but fails to create a proxy connection for the on premise public folders.

The error I get is a certificate mismatch, it seems that when a user on the LAN accesses Outlook/Exchange it is using a different certificate vs. when Outlook is launched on a WiFi network.

When I look at the Outlook connection information, I see the connection to outlook.com for ad/live/archive mailbox but no entry for public folder connection.

Our on premise Exchange is 2010 SP3 with latest CUs. The client is a domain joined laptop with Windows 7 and Office 2010 SP2, latest windows updates applied. Our infrastructure has a working ADFS 3 and DirSync setup for Office 365. My question then is, what do I need to do to make sure that the Cloud user launching Outlook on the LAN uses the proper certificate (the wildcard 3rd party cert.. vs. the self signed certificate which it looks like it may be using during the connection attempt).