rmail-nonignored-headers

rmail-nonignored-headers is a variable defined in `rmail.el'.
Its value is

"^x-spam-status:"

Documentation:
Regexp to match X header fields that Rmail should show.
This regexp overrides `rmail-ignored-headers'; if both this regexp
and that one match a certain header field, Rmail shows the field.
If this is nil, ignore all header fields in `rmail-ignored-headers'.

This variable is used for reformatting the message header,
which normally happens once for each message,
when you view the message for the first time in Rmail.
To make a change in this variable take effect
for a message that you have already viewed,
go to that message and type M-x rmail-toggle-header twice.

You can customize this variable.