feedmail-nuke-body-in-fcc

feedmail-nuke-body-in-fcc is a variable defined in `feedmail.el'.
Its value is

nil

Documentation:
If non-nil remove body of message in copies saved via Fcc:.
If a positive integer value, leave (up to) that many lines of the
beginning of the body intact. The result is that the Fcc: copy will
consist only of the message headers, serving as a sort of an outgoing
message log.

You can customize this variable.