I would suggest you get a hotmail / outlook account for access to current office online. If you need a desktop app, I would recommend LibreOffice.

Are you trying to use 07 outlook as the mailto app? If so, have a look at another user wanting to use 2010. https://support.mozilla.org/en-US/questions/1525395#answer-1752185

Are you trying to open a link from a message in Outlook 2007? What happens when you click the link -- are you getting this old problem:

https://www.slipstick.com/problems/this-operation-has-been-cancelled-due-to-restrictions/

Note that the suggestions there might not be up-to-date for Windows 10, but the diagnosis of Outlook looking for the old program folder when that has changed for some reason typically is still the issue.