What is this actually doing? I.e. are the emails being edited on the server or is the extension storing a set of edits and applying them when you view the edited emails in Gmail in Chrome? Are the original emails still accessible? How?
We are storing the changes you make to an email and then loading those changes back in when you view that email. The original email is never deleted, you can always click the "Restore" button get back to the original.
Storing them where?
We're currently using Firebase as our datastore.
Why not use a local datastore on the user's browser, like IndexedDB? I see no reason at all to install this and send my data to your external datastore when the same can be accomplished locally.
OP, please deliver. It is super important to me that the original emails are preserved somewhere. Is this so?