Well OK, so it's a semi-dumb question. But if we're going to assign
"magic meaning" to something, why not assign "magic meaning" to the null
address *specifically*in*the*context*of*SMTP*message*delivery*strategy*,
i.e. auto-fail messages destined for the null address and never retry them?
To nitpick your standards point about the null address, Section 2.5.2 of
RFC 4291 says that the IPv6 null address (which it idiomatically calls
"the unspecified address")
"must not be used as the destination address of IPv6 packets or in IPv6
Routing headers"
which effectively amounts to "no service here". Can't get there.
I haven't gone back to see if the IPv4 null address has been similarly
clarified/redefined, because, who still uses IPv4 anyway? :-)
- Kevin
On 7/23/2014 9:54 AM, Tony Finch wrote:
Kevin Darcy <k...@chrysler.com> wrote:
Potentially dumb question: what does this "magic meaning" MX target (".")
offer, that a target resolving to a null address (0.0.0.0 and/or ::0) does
not? No protocol or code changes required.
A target of "." causes an immediate permanent failure, whereas a tagret
that resolves to 0.0.0.0 is likely to cause retries and eventual timeouts.
The null address does, after all, mean "no service offered here".
No, it means "this host" - see RFC 3330.
Tony.
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