feedmail-nuke-bcc-in-fcc

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

nil

Documentation:
If non-nil remove [Resent-]Bcc: lines in message copies saved via Fcc:.
This is independent of whether the Bcc: header lines are actually sent
with the message (see feedmail-nuke-bcc). Though not implied in the name,
the same Fcc: treatment applies to both Bcc: and Resent-Bcc: lines.

You can customize this variable.