Heho, Just a followup as this is live now; You can also start a test at https://email-security-scans.org/ ;
If you select 'store received mails' you can download the messages we got from you (on various MX configured to have v4 only/v6 only/dual-stack) and check how they were delivered by the delivered-to headers (v4/v6). With best regards, Tobias
