It is a known issue that Outlook 2016 cannot connect to Exchange 2007. Also you can experience issue wint app LEAP. Here are the steps to switch back to Office 2013 as a temporary workaround:
1. Use the Fix it tool to remove the current Office 2016. See: Uninstall Office 2013, Office 2016, or Office 365 from a Windows computer
2. Install Office 2013 via the URLs below:
For Office 365 Business or Office 365 Business Premium: 32-bit, English: https://c2rsetup.officeapps.live.com/c2r/download.aspx?productReleaseID=O365BusinessRetail&platform=X86&language=en-us&version=O15GA&source=O15OLSO365
64-bit, English: https://c2rsetup.officeapps.live.com/c2r/download.aspx?productReleaseID=O365BusinessRetail&platform=X64&language=en-us&version=O15GA&source=O15OLSO365
For Office 365 Enterprise E3 or Office 365 ProPlus:
32-bit, English: https://c2rsetup.officeapps.live.com/c2r/download.aspx?productReleaseID=O365ProPlusRetail&platform=X86&language=en-us&version=O15GA&source=O15OLSO365
64-bit, English: https://c2rsetup.officeapps.live.com/c2r/download.aspx?productReleaseID=O365ProPlusRetail&platform=X64&language=en-us&version=O15GA&source=O15OLSO365
**Important: After you have rolled back to Office 2013, make sure you read this article to prevent Office 365 ProPlus/Office 365 Business from automatically updating to Office 2016 directly from the internet. "Method 2" in the article may applies to you.