I am not missing emails, after finding the mails in Outlook for Windows I could locate them by date & time in my Outlook for Mac - no - I did not need to check the other folders, it was in the right folder within the online archive - just it was not found by simple search request (only 20+ or so where found, 300+ or so not at all (like it did search only to a limited amount of records) - no third party email on Outlook for Mac - it is an exchange account (on our corporate Exchange 2010 Servers).

The new Outlook for Mac includes: Better performance and reliability as a result of a new threading model and database improvements. A new modern user interface with improved scrolling and agility when switching between Ribbon tabs. Online archive support for searching Exchange (online or on-premises) archived mail. Description: We have 3-4 Mac users who had Outlook 2011 for Mac and could find the In-Place Archive on the Outlook Pane. Now after upgrading to 2016 i.e. MS Office 365 Pro Plus subscription, the In-Place archive cannot be found.