gnus-body-boundary-delimiter

gnus-body-boundary-delimiter is a variable defined in `gnus-art.el'.
Its value is

"_"

Documentation:
String used to delimit header and body.
This variable is used by `gnus-article-treat-body-boundary' which can
be controlled by `gnus-treat-body-boundary'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.