Our current on premise Exchange infrastructure is Exchange 2010 SP3.  To deploy a hybrid infrastructure with Office 365 (version 15), will I need an Exchange 2013 CAS server for federated free\busy and mailbox migration?  Or can I leave everything as is Exchange 2010 SP3 and proceed with a hybrid configuration.

Another question, Id like to know is that our current O365 tenancy is version 15.  Would it be possible to request a O365 tenancy that is at version 14 in place of what we currently have?

Hi,

This IT Professional forum is for general questions and feedback related to Office Client. Since your question is more related to Office 365, I'd recommend you post a new question in the Office 365 Community forum for further assistance:

http://community.office365.com/en-us/f/default.aspx

The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding.

Steve Fan
TechNet Community Support