message-followup-to-function

message-followup-to-function is a variable defined in `message.el'.
Its value is

nil

• This variable may be risky if used as a file-local variable.

Documentation:
If non-nil, function that should return a list of headers.
This function should pick out addresses from the To, Cc, and From headers
and respond with new To and Cc headers.

You can customize this variable.