[Outages-discussion] [outages] CableOne DNS issue?

[Jeremy Chadwick]

With regards to the first paragraph only: SMTP MTAs, per RFC 5321 Sec 5,
should attempting connect to the DNS A record of the recipient domain.
In other words: an MX record isn't necessarily required for SMTP flow
(it's always highly recommended, however).

Of course, if the MX record would normally point to an FQDN which has a
different A record than the domain itself, then that would certainly
cause problems.  Same goes for if the authoritative NSes aren't
resolving the domain's A record at all (your second paragraph).

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Making life hard for others since 1977.             PGP 4BD6C0CB |

On Fri, Mar 24, 2017 at 09:27:01PM -0500, frnkblk--- via Outages wrote:
> Was just alerted that our outbound email queues have a few messages to
> cableone.net queued up, because there's no MX record (even Google and
> OpenDNS don't have an MX record cached).
> 
>  
> 
> DNSInspect (http://www.dnsinspect.com/cableone.net/10059114) is showing that
> their two nameservers aren't resolving their A record.
> 
>  
> 
> DownDetector is reporting issues: http://downdetector.com/status/cable-one
> 
>  
> 
> There's also few posts on Twitter, too: 
> 
> https://twitter.com/lucky_boym/status/845441576973295616
> 
> https://twitter.com/AnonySerb/status/845441954599092224
> 
>  
> 
> And just now posted, from CableONE:
> 
> https://twitter.com/cableONE/status/845460682560688128
> 
>  
> 
> Frank
> 

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