[O] [contacts] No completion in Gnus

[Thorsten]

Hello List, 
I have a org-contacts file with a few contacts with EMAIL property,
taken from gnus using org-capture as described in the org-contacts
manual. The contacts are tagged with some tags. But if I try to send an
email to one of the contacts using completion in message-mode, nothing
happens. I type + and press <TAB> in the To: header, but to no avail. I
even restarted Emacs without loading bbdb, since there seemed to be some
interference, but that didn't help either. I cannot find any more variables to
connect org-contacts with gnus, so I guess it should work out of the
box. 

What might be wrong in this case?
Thanks for any hints. 

PS
One further org-contacts related question: there is a predefined
property ADDRESS, without any inner structure. Am I supposed to write my own
org-capture template for that property? How would that look like - just
one single string? If I want something more structured (street, city,
zip-code etc), I have to define one property for each info-piece, or is
there something like a compound property? 

-- 
Thorsten