On 7/11/23 4:26 AM, Jaroslaw Rafa via mailop wrote:
TECHNICALLY, any email (there is no technical difference if it is B2B
or not) requires only a machine that has an A record and a running
MTA.
I'll wager a lunch that A records aren't even required. Maybe not any
name resolution at all. Things like /etc/hosts and NIS(+) for
resolution aside.
The thing that I was thinking about when I wrote my longer email was
businesses explicitly configuring email routing in their MTA such that
messages for a given destination domain were routed to a specified IP
address or even host name. That IP address, or hostname, can be locally
significant and not known by anyone outside the organization.
This type of bidirectional configuration would only be done between
organizations expressly trying to make sure that messages didn't flow
through the open Internet. The most likely entities to do this are
businesses.
Yes, individuals can do this, I've done it with friends as a proof of
concept. But such individuals are such the minority as to be a rounding
error.
And I understand Grant was writing from a technical, and not
administrative point of view.
I think that the pair of entities explicitly configuring their MTA to
route email to the others MTA independently of MXs also speaks to
administrative points of view. After all, it was likely a business
decision / administrative decision that prompted the desire to do such.
You can mail to username@hostname.domain, you don't need to have a
MX record. MX records are just a convenience so you can mail to
username@domain instead of username@hostname.domain.
Agreed.
I'll add that TCP/IP networks don't /need/ nor /require/ a *default*
gateway. They just need a route, whatever that route is. It can be an
explicit route solely for the destination which doesn't apply to any
other destination.
I've found that what the vast majority of what people do is a
significant subset of what is possible to do that it's not even funny.
What's worse is that -- in my opinion -- too many people fail to
understand that there are options that don't require doing what others
do, e.g. MX record for email or default gateway for IP routing.
These are Google requirements, not SMTP protocol requirements. We
should not confuse one with the other.
I absolutely agree.
Google, et al., have chosen to configure their email servers to require
things that the SMTP protocol does not require to function.
Each postmaster is free to configure their server(s) as they / their
organization sees fit to do so. But that does not make such
configuration good.
Grant. . . .
_______________________________________________
mailop mailing list
mailop@mailop.org
https://list.mailop.org/listinfo/mailop
