On 24Jul14, Kevin Darcy allegedly wrote: > So, if the TTL on the record were higher than the queue-expire setting > of the MTA, wouldn't the *intelligent* strategy be to promote the > tempfail to a permfail?
Most SMTP clients use a DNS cache so they have no idea what the original TTL is. Even if they could see the auth TTL you'd have to worry about domains that just happen to have very large TTLs in place today for whatever reason. How do you differentiate those domains? As far as standardizing such an idea, I'd hazard a guess that the IETF would not look kindly on encoding semantics into TTL values. Your rationale for this approach would need to be pretty compelling. > I've never written an MTA, but it seems like an > obvious optimization to me. It's surprising how hard it is to get the TTL out of most DNS client libraries. None of the gethostby* family return it. Even fancy libraries like c-ares are hit and miss with making the TTL available for different RR types. And of course the whole thing implies changing every SMTP client on the planet to recognize these large TTLs. That's a bit of work. All in all it's hard to see what this approach achieves compared to nullmx which works today with no code changes and does not require any special interpretation of DNS data. Mark. _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
