Tony Finch <[EMAIL PROTECTED]> wrote: > On Wed, 16 Apr 2008, Ned Freed wrote: >> On Tue, 15 Apr 2008, Arnt Gulbrandsen wrote: >> >>> I doubt that it makes sense to accept email from [EMAIL PROTECTED] >>> on a system that can only communicate with IPv4 addresses.
(It would help to be clear whether "from" refers to HELO, MailFrom, or some miscellaneous header.) >> In a single system case with fully symmetric routing, perhaps not. >> But as I mentioned previously, there are many cases where multiple >> systems with highly asymmetric routing are used to provide a mail >> service. Absolutely (for any of the cases I listed). >> In such a setup it is entirely possible that a system hosting an >> inbound MTA would have DNS query access but no outbound IPv6 access >> even if such access exists somewhere else in the setup. We would be ill-advised to assume even that IPv4-only systems have no reason to query (and perhaps even use in some fashion) AAAA RRs. > Of course, but in that case the postmaster would know that it is > possible to communicate indirectly with IPv6 addresses and would > therefore not disable IPv6 DNS lookup support. (We're really talking about an implementation detail outside the spec here.) In a legacy IPv4 system _right_now_ suppressing AAAA RRs might make sense. I do not agree it makes sense next year. Even if the postmaster _today_ does not know of a host speaking both IPv4 and IPv6 that will agree to relay his/her email, that doesn't mean that software like Exim shouldn't give an error message describing the problem as lacking a path to reach an IPv6 address. -- John Leslie <[EMAIL PROTECTED]>
