I was initially using a gmail account on this service.
Upon loggin into the dynv6 website (finally, after the week-end’s outage), I noticed that it was requesting me to revalidate my e-mail to keep my account.
But no matter what I tried, I haven’t received an e-mail, neither in my inbox, nor in the spam folder.
No sign of an e-mail ever been sent.
Today I tried switching my account to different e-mail by my service provider (infomaniak.ch) on a domain that I own, and the confirmation worked immediately.
Have other people noticed e-mail coming from dynv6 being rejected silently by Google?
(Maybe they have decided to ban e-mail coming from dynamic host domains, because some stupid reason like “protecting users from potential zombie bot”