Ok, error msg has gone away, but dspam isn't called at all.
This is part of my config:
$rcmail_config['markasjunk2_spam_cmd'] = '/usr/bin/dspamc --user dspam --class=spam --source=error --signature=%xds';
If I call su www-data -c "/usr/bin/dspamc --source=error --class=spam --user dspam --signature=bla"
dspam runs nice, except the signature not found, of course.
Also, even if I set debug to true, I can't find any log containing something of interest.
Can you pls help once more?