message-draft-coding-system

message-draft-coding-system is a variable defined in `message.el'.
Its value is

utf-8-emacs

Documentation:
*Coding system to compose mail.
If you'd like to make it possible to share draft files between XEmacs
and Emacs, you may use `iso-2022-7bit' for this value at your own risk.
Note that the coding-system `iso-2022-7bit' isn't suitable to all data.