In case you missed it, this week Microsoft released the new Office suite: Office 2016. Of course the latest version includes an updated version of Outlook too. Many people are eager to explore the new version of Office and others found their Office was automatically updated to Office 2016. From an Exchange perspective it’s important to be aware of the fact that Outlook 2016 does not support connections to Exchange 2007.
Customers who upgrade to Outlook 2016 and try to connect to their Exchange 2007 mailbox see this error message presented: The resource that you are trying to use is located on an unsupported version of Microsoft Exchange. Contact your e-mail administrator for assistance
This information can of course be found in the Office System Requirements, but you have to look for it:
Technically speaking there are workarounds available such as have Outlook 2016 access the Exchange 2007 server with the IMAP4 or POP3 protocol, but this of course introduces serious limitations and is not comparable with connecting through a MAPI or Outlook Anywhere connection.
Microsoft released an article which describes this issue and instructs Office 365 Personal, Office 365 Home, or Office 365 University users who's Outlook was automatically upgraded to Outlook 2016 to contact Microsoft Support to assist with a roll-back to Office 2013. See Error: Unsupported version of Microsoft Exchange error when you use Outlook 2016 to connect an Exchange 2007 account.
By the way, if your organization is still using Exchange 2007 you may want to look into an upgrade to a more recent Exchange version or Exchange Online. Exchange 2007 is in the Extended Support phase since 2012 and will go out of support in April 2017.