| Noun | 1. | mail service - the system whereby messages are transmitted via the post office; "the mail handles billions of items every day"; "he works for the United States mail service"; "in England they call mail `the post'"communicating, communication - the activity of communicating; the activity of conveying information; "they could not act without official communication from Moscow" snail mail - any mail that is physically delivered by the postal service; "email is much faster than snail mail" | |