Def. 2: Where a person carries on at length about a desired topic in the form of an email. Often not actually making a point about anything at all. And often sent to a close friend, co-worker, or confidant.
Edward: Obviously. You were email-rambling about that guy who never called you from last weekend.
Ingrid: Oh, right. Thanks for the reminder.
Edward: Sorry. Email-ramble all you want. We all do it.