gnus-button-message-level

gnus-button-message-level is a variable defined in `gnus-art.el'.
Its value is

5

Documentation:
*Integer that says how many buttons for news or mail messages will appear.
The higher the number, the more buttons will appear and the more false
positives are possible.

You can customize this variable.

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