On 7/11/23 2:48 PM, John Levine via mailop wrote:
If your From: domain has neither an A nor an MX, I don't think
you're going to get much mail of any sort delivered.
I believe it's possible for two entities to configure their email
servers to exchange email with each other without the use of DNS.
E.g.:
- IBM configures their email servers to send all @lotus.example email
to lotusmail which resolves via /etc/hosts to 192.0.2.1
- Lotus configures their email servers to send all @ibm.example email
to ibmmail which resolves via /etc/hosts to 198.51.100.5
Ergo IBM and Lotus can exchange @ibm.example and @lotus.example email
with each other without the use of DNS.
This would most likely be done in a business-to-business partner type
configuration where companies wanted to make sure that such B2B
communication did NOT traverse the public Internet.
Presuming of course that IBM and Lotus had some sort of private
connection and routing between each other.
I know that this is very far off the beaten path. But I believe it's
germane to discussions about what is and is not possible with email as
well as what are the minimum requirements.
I believe truly understanding these fringe cases help elaborate and
foster a better understanding of what is more common.
Grant. . . .
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