How do I register an ipv6 mailhost? Trying to parse   host 2002:a17:902:6881:0:0:0:0 (getting name) no name 0: Received: by 2002:a17:902:6881:: with SMTP id i1-v6mr7121788plk.323.1516767567431; Tue, 23 Jan 2018 20:19:27 -0800 (PST) No unique hostname found for source: 2002:a17:902:6881:0:0:0:0 Possible forgery. Supposed receiving system not associated with any of your mailhosts Will not trust this Received line. Mailhost configuration problem, identified internal IP as source Mailhost:
Please correct this situation - register every email address where you receive spam No source IP address found, cannot proceed.