A written message sent to a named address across a network. Addressed, kept, and answerable.
A twentieth-century compound of electronic (from Greek ēlektron, amber) and mail (Old French male, a bag or wallet, of Frankish origin); a message carried the way a bag once carried letters, only faster.
A written message sent to a named address across a network, kept and answerable the way a letter always was. What changed is only the speed of the carrying.