Basically, GNUS is not designed to be preloaded. For instance, if you
preload `gnus.el', some user variables which are initialized from
environment variables may be improperly initialized according to your
environment definitions. The variables gnus-nntp-server,
gnus-author-copy, and gnus-article-save-directory are such
variables.
To prevent GNUS from being initialized from your definitions, you
should unsetenv related environment variables before preloading
GNUS, or set the variables to nil after loading GNUS.