-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi, On 14/10/18 19:04, Rick Moen via luv-talk wrote:
Quoting Andrew McGlashan (andrew.mcglashan@affinityvision.com.au):
I'm not positive, but I think if mail is in the queue and resolution for the domain name isn't forthcoming due to possible down DNS server(s), then the mail will stay in the queue and it will be tried for delivery later with fresh DNS requests as well (in terms of mail when it comes to DNS answers). Of course, finding a server for other services (web for instance) would be an immediate problem when the TTL expires.
Could be right. I'd not embarrass myself by saying your guess is right or wrong without checking. ;->
Being specific about scenarios, here: I'm pretty sure that any newly generated mail that triggers a DNS lookup that gets immediate socket failure on all auth nameservers is going to get immediate 45x hard fail.
Hmm, a test mail to a non-existent FQDN is a logically identical case, wouldn't you agree? I could be missing something, otherwise, it would appear that in the scenario I describe the failure is immediate.
It might not be so easy to test. The name servers for a domain name are "glued" in the system, so to speak. That is, the authoritative IP address to use for name servers need not necessarily have an "A" RR associated with it. The upstream registry has to know where (IP address) to get answers from for the domain name. If you have "A" records (as you would normally do), then you can make DNS queries using those servers using the IP given by the A record. dig @ip.ad.dr.es -t a mail.unknown.net So, you need a domain name that has no name servers assigned whatsoever or you need to deliberately take the name servers down; neither of which I plan to do right now, but I might test further at another time with a less significant domain name. Using a random and otherwise non-existent domain name will give you an immediate fail though. Cheers A. -----BEGIN PGP SIGNATURE----- iHUEAREIAB0WIQTJAoMHtC6YydLfjUOoFmvLt+/i+wUCW8L+OAAKCRCoFmvLt+/i +wcvAP9hTQKL4+ish0aIGUT2x534FjrBkbL1FjD5e3YdhiHtGwD/Q2q9ydnAZDtu 7if9WfH707O3LeNnnLTVqFMBnJZBFVA= =5peL -----END PGP SIGNATURE-----