rmail-search-mime-header-function

rmail-search-mime-header-function is a variable defined in `rmail.el'.
Its value is

nil

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

Documentation:
Function to check if a regexp matches a header of MIME message.
This function is called by `rmail-message-regexp-p-1' if
`rmail-enable-mime' is non-nil. It is called (with point at the
start of the header) with three arguments MSG, REGEXP, and LIMIT,
where MSG is the message number, REGEXP is the regular
expression, LIMIT is the position specifying the end of header.