Hi Janus,
Thanks for your pointers. All clear except for finding the right parameter for the tcl command convertto.
For starters, the header_subject is fine, thats not the one that needs convertion, since all accents and such remain intact. My concern is the body of the message.
I tried convertto on multiple locations (before creation new mail, before sending, within acs_mail_body_to_output_format, etc), all to no avail.
set content [encoding convertto iso8859-1 $content]
Now I presume that iso8859-1 is what I should use, since I couldn't find a good explanation online. But unfortunatly it doesn't work.
The mail headers all look proper, but the body output is still wrong.
Any clue?