TL;DR
Soon we will offer IPv6 only email services. So far it has been decided that the SMTP part will be IPv6 only, the IMAP/webmail part might be dual stack or IPv6 only as well.
Next generation services - going one step further
When you know us, you know that we have been pushing IPv6 only services since 2017. IPv6 only VMs - we got it. IPv6 only websites - we got it. IPv6 only routers and networks? We got plenty of them.
Now we played a bit with the though of, what if there was an email domain that can only receive emails from IPv6 capable hosts? It would certainly be a challenge, but more for the legacy only providers, not for us.
So stay tuned and expect an IPv6 only email service soon to be available.