I’ve noticed my niece do this on facebook. “Someone inbox me” which I assume to mean “Someone initiate a facebook message conversation with me”
To my 31 year old mind an inbox is well established as being a folder in an email client that serves as the first port of call for newly received unsorted emails. Thus it looks wrong to see the word ‘inbox’ used differently.
Since at least 1993, since that’s when I started working at a bank and using email extensively, and it was called an “inbox” there. The metaphor was drawn directly from the original meaning you cite, as was the metaphor for “desktop,” “trash can,” “folder,” and dozens of other computer interface terms.
I think Inner Stickler was poking fun of Lobsang for complaining about the definition of ‘inbox’ expanding while (apparently) not realizing that his own electronic based definition was an expansion of its original physical reality-based definition.
I regret to announce that the use of “inbox me!” has spread beyond facebook. I received an email from a film extra agency which invited me “to inbox” if I was interested. It sounds snappy and hip and retarded. I deplore it.