How to make Emacs Gnus to get new mails automatically?

[ST]

Hello,

I try to fetch new mails with Gnus, but it doesn't work. I tried
following options in my `.emacs` file:

    ;(setq gnus-demon-timestep 10)
    (gnus-demon-add-handler 'gnus-group-get-new-news 1 nil)
    ;(gnus-demon-add-handler 'gnus-demon-scan-mail 1 nil)
    ;(gnus-demon-add-handler 'gnus-demon-scan-news 1 nil)
    (gnus-demon-init)

I tried to add each of the 3 handlers, and put `t` instead of `nil`, but
it didn't work. If I press `g` or run `M-x gnus-group-get-new-news`
manually Gnus does fetchs new mails. I checked `gnus-demon-handlers` and
it indeed says: `gnus-demon-handlers's value is
((gnus-group-get-new-news 1 nil))` but it doesn't fetch mails
automatically.

Thank you!!
Just in case: the question is also here:
http://stackoverflow.com/questions/38100542/how-to-make-emacs-gnus-to-get-new-mails-automatically