gnus-auto-expirable-marks

gnus-auto-expirable-marks is a variable defined in `gnus-sum.el'.
Its value is

(75 114 67 89 79 82 77)

Documentation:
*The list of marks converted into expiration if a group is auto-expirable.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.