gnus-group-find-new-groups). With 1 C-u, use the
ask-servermethod to query the server for new groups. With 2 C-u's, use most complete method possible to query the server for new groups, and subscribe the new groups as zombies.
gnus-group-expire-articles). That is, delete all expirable articles in the group that have been around for a while. (see Expiring Mail).