[Top] [All Lists]

Re: current usage of AAAA implicit MX?

2008-04-05 13:21:30

Peter J. Holzer writes:
On 2008-04-04 17:30:29 -0400, Robert A. Rosenberg wrote:
RFC 3974
It, BTW, REQUIRES an MX if there are any IPv6 MTAs and only supports A-Fallback in the absence of an MX


"For the transition period, all mail domains should have MX records such that MX targets with IPv4 and IPv6 addresses exist"?

 It also states that in the presence of an MX containing IPv6 address
 references, an IPv4-Only stack should ignore the IPv6 addresses

Yes, of course. It cannot reach them anyway. Just as IPv6-only hosts can ignore A records since they cannot reach them either.

An IPv6-only host must use the presence/absence of A records to generate the DSN. The DSN status code is 5.1.2 if there's no A and 5.4.x if there is an A but no way to reach it (ie. no configured relay).