I saw the headline for this article and thought, "wtf, e-mail just worked over IPv6 from the time I put the AAAA record in the DNS". But I went ahead and had a look, and it is actually pretty interesting: http://engineering.linkedin.com/email/sending-and-receiving-emails-over-ipv6
Actually, it's even more complicated than that. I need to send mail directly instead of "use the provider relay" because the provider relay doesn't allow me to check whether mail is still queued - not all the world has reliable mail delivery, unfortunately and for the people I work with, this is an issue. For IPv4, it's easy for an ISP to set up stub forward & reverse records and that's what I got away with for many, many years. For IPv6, the situation is different. As discussed, users have more than one address and hence may need need more than one forward/reverse pair, and the address may not be predictable. This gives new problems: * If the connection is big enough to warrant delegation, then making FCrDNS work for IPv6 is doable. For small businesses and home power users however, this may not be feasible. * Making forward & reverse match for every /48 of every customer is a challenge; * Delegating may not be feasible. How do you delegate to "John's pet animal and sushi shop"? The guy probably doesn't run a DNS server to delegate to.. * Making Dynamic DNS updates work between ISP and customer is a challenge at best; * I have not seen any portal solutions, to let the customer handle this. Even with XS4all, for whom I am a customer, doesn't have an automated way for this and the current workaround involves manual intervention with all it's nasty scaling properties. * I don't think that customer-specific subdomains and SPF-records will scale either. I don't hear much of this new, IPv6-specific problem. Comments? Geert Jan