> I implemented this, but found some problems. If I encode the subject like
> 
> Subject: =?ISO-8859-1?Q?åøæ?=
> 
> it displays well unde MS Outlook, but not under Mozilla Thunderbird or pine,
> which both display the full text (including the ISO...). So it looks like
> there is no single solution which satisfies all mail programs. It should at
> least work for Outlook and Thunderbird, so if anyone has an idea please let me
> know.

If I read the RFC correctly when you use B encoding you are using BASE64 encoding.
Maybe that could be a solution?

Best regards
Michael