Crossword puzzle clue "portion of an editor's mail"

Portion of an editor's mail

Meet portion, or portion of meat

Portion portion

A crossword editor has to be very careful when changing one--unlike this puzzle's editor, who was careless four times herein

Forgets to mail the mail, say

They come after signatures in snail mail, yet before signatures in e-mail: Abbr.

___ mail (e-mail folder)

___ mail (e-mail alternative)