> The true innovator in the e-mail space has been GMail, which has brought things like autosave,

Small nit, Outlook 2003 had AutoSave. GMail was publicly introduced in 2004.

> embracing the fact that it is not truly productive to file every single e-mail into a purposeful folder

That's the "Inbox"

> embracing that tagging is better than folders.

I'm pretty sure that Outlook has had categories (the color-coded custom named things that can be multiply applied to emails) since 2000ish.