Don't get me wrong. I'm not saying people should ignore the RFC1035 standards. I'm just saying its possible. The one's I'm aware of are all companies using 'In-House' mail systems designed to either keep the mail staying in-house, and/or prevent outside mail from getting in.
But, as pointed out, this group should be following the RFC1035 standard.
---------- Wm Lewis (KG6BAJ) AMPR Net IP Address Coordinator - Northern and Central California Regions (A 100% Volunteer Group) (530) 263-1595 (Home/Office) ______________________________________________
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At 03:48 PM 5/27/2015, you wrote:
(Please trim inclusions from previous messages) _______________________________________________ On Wed, May 27, 2015 at 3:41 PM, William Lewis kg6baj@n1oes.org wrote:
Where you say "Owners, please update them with a proper hostname instead of the literal IP address." I would like to point out that it is entirely possible to have an IP address that has no HOSTNAME assigned to it at all. The most common are used for mail. I use 2 that are setup this way for security reasons.
MX records must point to a hostname. Here's a good description of why: http://serverfault.com/a/663122
But the bottom line is: it's the spec.
Tom KD7LXL _________________________________________ 44Net mailing list 44Net@hamradio.ucsd.edu http://hamradio.ucsd.edu/mailman/listinfo/44net
Here is a case where RFC's conflict.
RFC5321 in Section 5 [http://tools.ietf.org/html/rfc5321#section-5] states:
"The lookup first attempts to locate an MX record associated with the name. If a CNAME record is found, the resulting name is processed as if it were the initial name.*"*
To add to the fun, a couple lines further into the paragraph states that:
" If an empty list of MXs is returned, the address is treated as if it was associated with an implicit MX RR, with a preference of 0, pointing to that host."
So technically, every A record must be treated as a capable mail exchanger even if there are no MX records.
We could just axe all the MX records.
On Wed, May 27, 2015 at 3:59 PM, William Lewis kg6baj@n1oes.org wrote:
(Please trim inclusions from previous messages) _______________________________________________ Don't get me wrong. I'm not saying people should ignore the RFC1035 standards. I'm just saying its possible. The one's I'm aware of are all companies using 'In-House' mail systems designed to either keep the mail staying in-house, and/or prevent outside mail from getting in.
But, as pointed out, this group should be following the RFC1035 standard.
Wm Lewis (KG6BAJ) AMPR Net IP Address Coordinator - Northern and Central California Regions (A 100% Volunteer Group) (530) 263-1595 (Home/Office) ______________________________________________
This message is for the designated recipient only and MAY CONTAIN PRIVILEGED OR CONFIDENTIAL INFORMATION. If you have received it in error, please notify the sender immediately and delete the original. Any other use of this E-mail is prohibited.
At 03:48 PM 5/27/2015, you wrote:
(Please trim inclusions from previous messages) _______________________________________________ On Wed, May 27, 2015 at 3:41 PM, William Lewis kg6baj@n1oes.org wrote:
Where you say "Owners, please update them with a proper hostname
instead of
the literal IP address." I would like to point out that it is entirely possible to have an IP address that has no HOSTNAME assigned to it at
all.
The most common are used for mail. I use 2 that are setup this way for security reasons.
MX records must point to a hostname. Here's a good description of why: http://serverfault.com/a/663122
But the bottom line is: it's the spec.
Tom KD7LXL _________________________________________ 44Net mailing list 44Net@hamradio.ucsd.edu http://hamradio.ucsd.edu/mailman/listinfo/44net
On 5/27/15 8:15 PM, Don Fanning wrote:
Here is a case where RFC's conflict.
They don't, re-read it.
RFC5321 in Section 5 [http://tools.ietf.org/html/rfc5321#section-5] states:
"The lookup first attempts to locate an MX record associated with the name. If a CNAME record is found, the resulting name is processed as if it were the initial name.*"*
This means if the lookup for www.example.com. returns CNAME example.com, it will use the MX records under example.com., not anything under the CNAME record www.example.com.
To add to the fun, a couple lines further into the paragraph states that: " If an empty list of MXs is returned, the address is treated as if it was associated with an implicit MX RR, with a preference of 0, pointing to that host."
So technically, every A record must be treated as a capable mail exchanger even if there are no MX records.
No. Only if there is no other MX record returned will it use the A record as a default. This is a last ditch effort, and there is nothing saying that a A record identified host needs to run a mail exchanger on it.
On Wed, May 27, 2015 at 5:27 PM, Bryan Fields Bryan@bryanfields.net wrote:
(Please trim inclusions from previous messages)
RFC5321 in Section 5 [http://tools.ietf.org/html/rfc5321#section-5]
states:
"The lookup first attempts to locate an MX record associated with the
name. If
a CNAME record is found, the resulting name is processed as if it were the initial name.*"*
This means if the lookup for www.example.com. returns CNAME example.com, it will use the MX records under example.com., not anything under the CNAME record www.example.com.
That is not true at all. The previous paragraph states that it must process the entire FQDN and not many any inferences as to the domain's relationship with the FQDN.
To add to the fun, a couple lines further into the paragraph states that: " If an empty list of MXs is returned, the address is treated as if it was associated with an implicit MX RR, with a preference of 0, pointing to that host."
So technically, every A record must be treated as a capable mail exchanger even if there are no MX records.
No. Only if there is no other MX record returned will it use the A record as a default. This is a last ditch effort, and there is nothing saying that a A record identified host needs to run a mail exchanger on it.
You are absolutely correct. You don't have to run a smtpd on it at all. It just states that where there is lack of a MX record that it should treat the FQDN of the mail as the MX with a preference of 0. If it doesn't connect then it goes through retry logic until it's dropped to the floor.
On 5/27/15 8:33 PM, Don Fanning wrote:
(Please trim inclusions from previous messages)
RFC5321 in Section 5 [http://tools.ietf.org/html/rfc5321#section-5]
states:
"The lookup first attempts to locate an MX record associated with the
name. If
a CNAME record is found, the resulting name is processed as if it were the initial name.*"*
This means if the lookup for www.example.com. returns CNAME example.com, it will use the MX records under example.com., not anything under the CNAME record www.example.com.
That is not true at all. The previous paragraph states that it must process the entire FQDN and not many any inferences as to the domain's relationship with the FQDN.
I'd like to try it out then, as I'm certain this doesn't work that way in most resolvers for MX's. I've run into it before even.
On Wed, May 27, 2015 at 5:36 PM, Bryan Fields Bryan@bryanfields.net wrote:
(Please trim inclusions from previous messages) _______________________________________________ On 5/27/15 8:33 PM, Don Fanning wrote:
(Please trim inclusions from previous messages)
RFC5321 in Section 5 [http://tools.ietf.org/html/rfc5321#section-5
]
states:
"The lookup first attempts to locate an MX record associated with
the
name. If
a CNAME record is found, the resulting name is processed as if it were the initial name.*"*
This means if the lookup for www.example.com. returns CNAME
example.com,
it will use the MX records under example.com., not anything under the
CNAME
record www.example.com.
That is not true at all. The previous paragraph states that it must process the entire FQDN and not many any inferences as to the domain's relationship with the FQDN.
I'd like to try it out then, as I'm certain this doesn't work that way in most resolvers for MX's. I've run into it before even.
I can tell you that GMail's MX RR's work in this fashion. I don't need to know their A record for my DNS. I just add their CNAME'ed MX records to my domain files and my mail shows up. And my domain isn't hosted by them. Just my mail hosting.
On 5/27/15 8:45 PM, Don Fanning wrote:
I'd like to try it out then, as I'm certain this doesn't work that way in most resolvers for MX's. I've run into it before even.
I can tell you that GMail's MX RR's work in this fashion. I don't need to know their A record for my DNS. I just add their CNAME'ed MX records to my domain files and my mail shows up. And my domain isn't hosted by them. Just my mail hosting.
Don, I've re-read the document, you might have a technical point here.
Can you send me a domain setup in this way now, I'd like to query it's records and see this in the wild.
Thanks,
On Wed, May 27, 2015 at 7:30 PM, Bryan Fields Bryan@bryanfields.net wrote:
Can you send me a domain setup in this way now, I'd like to query it's records and see this in the wild.
It should be fairly easy to sandbox it on your LAN with two sendmail boxes.
http://serverfault.com/questions/470649/how-can-e-mail-be-delivered-to-a-dom...
On 5/28/15 12:29 AM, Don Fanning wrote:
Can you send me a domain setup in this way now, I'd like to query it's records and see this in the wild.
It should be fairly easy to sandbox it on your LAN with two sendmail boxes.
http://serverfault.com/questions/470649/how-can-e-mail-be-delivered-to-a-dom...
This link has nothing to do with a CNAME record and MX following the actual A record.
I'm not full of free time to set this up, so if you have it working in the wild please share. If not it's just speculation about arcane RFC compliance; certainly not anything that would be best practice.
-
Bryan Fields -
Don Fanning -
William Lewis