Our company has developed a plugin for the desktop version Outlook (using VSTO) that automatically upload on our servers instead of sending then as regular attachment. For exemple, when the file is too large or contains some AIP sensitivity labels such as "confidential", theses files are uploaded on our servers with the plugin, and a link is added in the message body for download.
So my question is, is it possible to intercept when attachment are added with "Attach / Browse this computer" the same way it was possible with VSTO.
I have noticed that a popup is already displayed when files are too large, but only OneDrive is the only cloud provider available. Is it possible to register another cloud provider in this popup?