You're going to ask why a website dedicated to Dynamics GP development needs an article on Visual Studio Tools for Office (VSTO), right?
Give me a minute to sell you.
We do integrations. We recently did an application where the integration files arrived via email. The user either has to save the files manually, or... we write an Outlook addin that does it automatically. So, we write a VSTO add-in
This article contains a short code example of how to save files in Outlook automatically.