This is silly. There are hundreds of third-party add-ins for Microsoft Office. There are 677 listed in the Office Marketplace [1], including 20 "inbox management" applications.
Microsoft encourages third-party developers to write add-ins for Office. That doesn't mean they have any interest in acquiring (or copying) all of those add-ins.
Microsoft encourages third-party developers to write add-ins for Office. That doesn't mean they have any interest in acquiring (or copying) all of those add-ins.
[1] http://office.microsoft.com/en-us/marketplace/FX100621221033...