in fact the email app doesn't check for new emails at all!

I've got a dovecot imap server at home reachable over the net (using it for years now). I could connect and chose some favorit folders.
Now only the inbox is checked for new emails! But there is no sense on my configuration since no mail actually goes there.
I want to get notifications on the favorites folders but it even doesn't check those all 30 mins, 1 hours or whatever I tell him to do.
It only refreshes when I go into that folder...

Is there some workaround to get notifications about new emails in favorite folder?