feedmail-force-binary-write

feedmail-force-binary-write is a variable defined in `feedmail.el'.
Its value is

t

Documentation:
If non-nil, force writing file as binary (this applies to queues and Fcc:).
On systems where there is a difference between binary and text files,
feedmail will temporarily manipulate the value of `coding-system-for-write'
to make the writing as binary. If nil, writing will be in text mode.
On systems where there is no distinction or where it is controlled by other
variables or other means, this option has no effect.

You can customize this variable.