Outlook is currently undergoing a major redesign. This redesign is called 'New Outlook' and is currently in preview. This article explains how to use mail merge with the new Outlook.
First off: Yes, SecureMailMerge works with New Outlook without any restrictions. Our guides will show you familiar screenshots for New Outlook to get you started.
New Outlook is basically the same interface as Outlook on the Web, so the long term goal is to have one interface for all the Outlook functionality, but because Outlook for the Web has a smaller feature set than the classic Outlook on the Desktop Microsoft is playing catch-up with the features. Maybe some lesser used features will not find their way into the new Outlook.
It is as yet unclear if traditional mail merge using Word is supported in New Outlook.