Email Quotes and Inclusion Conventions

Early mail and netnews readers had no facility for including messages this way, so people had to paste in copy manually. BSD Mail(1) was the first message agent to support inclusion, and early Usenetters emulated its style. But the TAB character tended to push included text too far to the right (especially in multiply nested inclusions), leading to ugly wraparounds. After a brief period of confusion (during which an inclusion leader consisting of three or four spaces became established in EMACS and a few mailers), the use of leading > or > became standard, perhaps owing to its use in ed(1) to display tabs (alternatively, it may derive from the > that some early Unix mailers used to quote lines ...