I've got a macro for sorting my incoming e-mail that I considered converting to Office-JS. I just saw this SO post and the answer stated --
Outlook web add-ins work under the context of currently selected item only
Does that mean my idea of an Add-In that sorts e-mail is unfeasible currently? Can I make an Add-In that constantly runs and redirects incoming e-mails?
You can run add-in(s) only on a particular item(mail/calendar event). The Add-in framework does not support a trigger based on the incoming emails.