RFCs are supposed to make specific use of certain imperatives, as per RFC2119:
https://www.ietf.org/rfc/rfc2119.txt
SHOULD NOT and MUST NOT are used differently, where the former means something
is not recommended, and the latter means it is prohibited.
And yes, it's not good behavior to send from a domain you don't receive into,
but that does not make -all and NullMX the same.
Mike
-----Original Message-----
From: mailop <mailop-boun...@mailop.org> On Behalf Of Slavko via mailop
Sent: Thursday, May 25, 2023 1:34 AM
To: mailop@mailop.org
Subject: Re: [mailop] Microsoft Office365 not rejecting emails when instructed
so by SPF recored?
Dňa 24. mája 2023 22:41:01 UTC používateľ Graeme Fowler via mailop
<mailop@mailop.org> napísal:
>[moderator note]
>
>SPF asserts senders (by definition)
>NullMX asserts receivers (also by definition)
>
>Interpretation aside, the fact they are (mis?)understood to be the same thing
>is a clear conflation. It may be language based, it may not, but please stop
>splitting this specific hair.
I am confused now as in RFC 7505 sect. 4.2 one can read:
Null MX is primarily intended for domains that do not send
or receive any mail...
And:
...mail systems SHOULD NOT publish a null MX record for domains
that they use in RFC5321.MailFrom or RFC5322.From addresses.
I understand that RFC as: nullMX's primary purpose is about not receiving, but
as side effect it can result as not sending too.
Is my understanding wrong?
Of course, the sending is affected only if receiver checks return-path, but
that is the same with SPF as it is usefull only if SPF is checked...
regards
--
Slavko
https://www.slavino.sk/
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