If I read the thread so far correctly, Igor can't enable a single server
with v6, because the instant he updates the DNS so an MX for his domain
references a AAAA, that will become the preferred target for his domain
from the entire IPv6 world, and he's gonna need a load balancer from Day 0.
This was the whole point in using a separate domain name so that this
wouldn't happen. Having said that- I suspect every user in the current v6
Internet could hit his site and still not overwhelm a single server :)
There simply aren't that many of us :)
-Don