gnus-secondary-select-methods

gnus-secondary-select-methods is a variable defined in `gnus.el'.
Its value is

nil

Documentation:
A list of secondary methods that will be used for reading news.
This is a list where each element is a complete select method (see
`gnus-select-method').

If, for instance, you want to read your mail with the nnml back end,
you could set this variable:

(setq gnus-secondary-select-methods '((nnml "")))

You can customize this variable.