problems with gnus-posting-styles: groups.

[Uwe Brauer <oub@mat.ucm.es>]

Hello

I tried to change my gnus-posting-style setting, the
following works as expected.

      gnus-posting-styles
      '(((header "To" "oub@mat.ucm.es")
	 (name "Uwe Brauer")
         (address "oub@mat.ucm.es")
	 ("Reply-To" "Uwe Brauer <oub@mat.ucm.es>"))
	((header "To" "oub.oub.oub@gmail.com")
	 (name "Uwe Brauer")
         (address "oub.oub.oub@gmail.com")
	 ("Reply-To" "Uwe Brauer <oub.oub.oub@gmail.com>"))

however I now consider it better to change name, address and
reply to according to the group I am in, not according to the "To" headers.

So I tried 

(setq gnus-posting-styles
 '(("nnimap+gmail:INBOX" (address "oub.oub.oub@gmail.com"))))

And "nnimap+gmail:INBOX" is the name of the group in
question as (describe-variable 'gnus-newsgroup-name) found
out. But the setting did not work out as expected the header
looked like

,----
| To: 
| Subject: 
| Reply-to: Uwe Brauer <oub@mat.ucm.es>
| From: Uwe Brauer <oub@mat.ucm.es>
| Gcc: nnml+archive:sent-mail
| --text follows this line--
`----


I also tried "nnimap+gmail*" but it did not help.
What do I miss?

Thanks

Uwe Brauer