iso-8859-1 in outgoing messages in spite of UTF-8 environment

[Stein Arild Strømme]

I have 

  (set-language-environment 'UTF-8)

How can I still get message-mode to use iso-8859-1 in outgoing
messages?  (I get complaints about UTF-8 email.)  Looking at the info
nodes for Message is quite confusing on this, and the things I have
tried do no seem to work, things like

  (setq mm-content-transfer-encoding-defaults '(iso-8859-1))
  (setq mm-body-charset-encoding-alist '(iso-8859-1 . 8bit))
  (setq message-posting-charset 'iso-8859-1)

I have these variables:

  message-default-charset is a variable defined in `message.el'.
  Its value is iso-8859-1

  message-posting-charset is a variable defined in `message.el'.
  Its value is iso-8859-1

Grateful for any hints.

SA
-- 
Stein Arild Strømme            +47 55584825, +47 95801887
Universitetet i Bergen                  Fax: +47 55589672     
Matematisk institutt, UiB     http://math.uib.no/stromme/         
Johs Brunsg 12, N-5008 BERGEN         stromme@math.uib.no