A combat "sport" where two participants, generally of similar intellectual weight, fight each other via an e-mail exchange. Inboxing typically involves a series of one-to-one e-mail exchanges (called "rounds"); however, a popular and successful tactic is for one participant to fire off a "combination" of back-to-back e-mails before their opponent has time to respond to the first message. Victory is achieved if the opponent is knocked down emotionally and unable to get up (a Knockout or KO), or if the opponent's Inbox is deemed too overwhelmed to continue (a Technical Knockout, or TKO). If there is no stoppage of the fight before an agreed number of rounds, a winner is determined by judges' (those CC'd on the e-mail exchange) scorecards.
After several rounds of inboxing with her co-workers, Emily finally had agreement on the format for the marketing presentation.