I have verified with tcpdump that Amavis does provide an XFORWARD
command to the after-Amavis smtpd.
I have verified with tcpdump that the after-Amavis smtpd does connect to
opendmarc and that they have a (very short) dialog.
I don't know the milter protocol. The short dialog between the
after-Amavis smtpd and opendmarc contains "127.0.0.1" a few times, but
not the XFORWARD address, but I do not know if that is suspicious.
I would very much appreciate it if somebody can tell me what is going on
- and what opendmarc means with that error message.