gnus-article-unfold-long-headers

gnus-article-unfold-long-headers is a variable defined in `gnus-art.el'.
Its value is

nil

Documentation:
If non-nil, allow unfolding headers even if the header is long.
If it is a regexp, only long headers matching this regexp are unfolded.
If it is t, all long headers are unfolded.

This variable has no effect if `gnus-treat-unfold-headers' is nil.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.1 of Emacs.