gnus-auto-subscribed-groups

gnus-auto-subscribed-groups is a variable defined in `gnus-start.el'.
Its value is

"^nnml\\|^nnfolder\\|^nnmbox\\|^nnmh\\|^nnbabyl\\|^nnmaildir\\|^nnimap"

Documentation:
*All new groups that match this regexp will be subscribed automatically.
Note that this variable only deals with new groups. It has no effect
whatsoever on old groups.

New groups that match this regexp will not be handled by
`gnus-subscribe-newsgroup-method'. Instead, they will
be subscribed using `gnus-subscribe-options-newsgroup-method'.

You can customize this variable.