Following the thread "sign auto-reply vacation with OpenDKIM" , I read the MILTER_README where it's stated :
"Postfix currently does not apply content filters to mail that is forwarded or aliased internally, or to mail that is generated internally such as bounces or Postmaster notifications. This may be a problem when you want to apply a signing Milter to such mail." Since I have OpenDKIM signing my bounces I believe this was true up to some version. Instead it should mention that internal_mail_filter_classes should be set to bounce. José Borges Ferreira
