Several people in NANOG have opined that there are a number of mail
servers on the Internet operating with IPv6 addresses. OK. I have a
mail server, which has been on the Internet for decades. On IPv4.
For the last four years, every attempt to get a PTR record in ip6.arpa
from my ISP has been rejected, usually with a nasty dismissive.
Today, I'm trying again to get that all-important PTR record. If I'm
successful, then I expect to have my mail server fully up and running in
the IPv6 space within 72 hours, or when the DNS changes propagate,
whichever is longer.