Mailing List Archive

On 09/05/2022 09:53, Julian Bradfield via Exim-users wrote:
> Coming to the point: is the bounce message coming from some (hopefully
> experimental) part of Exim, or must it have been maliciously
> hand-crafted in a config file by the solardns administrators?
>
> I can't find anything relevant in the 4.95 docs.

Exim cares very little about headers. I'd go for
"hand-crafted", though I've not actually checked.
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Jeremy

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D?a 9. 5. o 10:53 Julian Bradfield via Exim-users napísal(a):
> I'd never seen this before, so I went off to check RFC5822, and I see
> that in the 5822 version, only one of the To:, CC: or BCC: headers is
> allowed to be generated.

RFC 5822 doesn't exists.

> However, the RFC says that implementations MUST accept the (now)
> obsolete syntax, and SHOULD treat multiple destination address headers
> in the obvious way.

I cannot find your citatinon nor in RFC5322 nor in RFC5321, which RFC do
you mean?

IMO, do not send multiple addressing headers, the both RFC are here for
about 25 years, and here is no reason to use syntax which was obsoleted
25 years ago nowadays.

regards

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On 2022-05-09, Slavko via Exim-users <exim-users@exim.org> wrote:
> D?a 9. 5. o 10:53 Julian Bradfield via Exim-users napísal(a):
>> I'd never seen this before, so I went off to check RFC5822, and I see
>> that in the 5822 version, only one of the To:, CC: or BCC: headers is
>> allowed to be generated.
>
> RFC 5822 doesn't exists.

My error - google autocorrected me to 5322 and I didn't
notice. (Happens every time...)

>> However, the RFC says that implementations MUST accept the (now)
>> obsolete syntax, and SHOULD treat multiple destination address headers
>> in the obvious way.

> I cannot find your citatinon nor in RFC5322 nor in RFC5321, which RFC do
> you mean?

The "MUST accept" is in the first paragraph of section 4., and is
repeated for emphasis in the immediately following Note.

The "SHOULD combine multiple headers" is in section 4.5.3.

> IMO, do not send multiple addressing headers, the both RFC are here for
> about 25 years, and here is no reason to use syntax which was obsoleted
> 25 years ago nowadays.

5322 is dated October 2008, which is 14 years. In something as
critical as mail, that's a short time. I might agree that we don't
need to accept bang addresses any more, but that's about as far as I'd
go :)

Anyway, the point is that (as I've seen), modern MTAs (the message in
question went through Postfix, then Sendmail) do not rewrite messages
with multiple addressing headers. The user has no way of knowing that
multiple CC: headers are deprecated, and it's a natural thing to
write if you're adding several distinct groups of people in cc.

An obsessively educational sysadmin could send a warning about it,
but rejecting messages that MUST be accepted remains clearly wrong!


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D?a 9. mája 2022 11:37:35 UTC používate? Julian Bradfield via Exim-users <exim-users@exim.org> napísal:

>My error - google autocorrected me to 5322 and I didn't
>notice. (Happens every time...)

No problem, it happens, only to be sure what was the typo, in that case, it was
nice, because one can guess the 5 as typo too (as RFC822 or as RFC2822)

>The "MUST accept" is in the first paragraph of section 4
>
>The "SHOULD combine multiple headers" is in section 4.5.3.

Found it, they both seems to be the same as in RFC2822...

>5322 is dated October 2008, which is 14 years. In something as
>critical as mail, that's a short time.

Sorry, my bad math. But both your citations appears in RFC2822 too, thus
they was deprecated in between your 14 years and my 25 (more precise 24)
years -- 21 years ago.

>Anyway, the point is that (as I've seen), modern MTAs (the message in
>question went through Postfix, then Sendmail) do not rewrite messages
>with multiple addressing headers.

Sure, change message on transport is mostly not OK, especially with DKIM,
but (some) fixing of messages is OK for MSA.

>An obsessively educational sysadmin could send a warning about it,
>but rejecting messages that MUST be accepted remains clearly wrong!

IMO not true. Their MTA = their responsibility = their rules and they cleanly
inform sender what is the problem.

Especially your second citation is SHOULD, thus not strictly required. And
consider, that there can bo other (than MTA) SW involved in (final) delivery
or processing, which simple do not support multiple destinations headers,
which can be reason for reject. But IMO, educating the users is good reason
too.

Consider, from the same RFC5322 section 4:

...these (obsolete -- context by me) syntactic forms MUST NOT be
generated according to the grammar in section 3, ...

Once again, fix client (message generation), instead of asking to support
obsolete things.

regards

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Slavko

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On 9 May 2022, at 09:53, Julian Bradfield via Exim-users <exim-users@exim.org> wrote:
<snip>
> Coming to the point: is the bounce message coming from some (hopefully
> experimental) part of Exim, or must it have been maliciously
> hand-crafted in a config file by the solardns administrators?
>
> I can't find anything relevant in the 4.95 docs.

It's not in the source code anywhere, so you're looking at a locally-generated bit of logic.

Their network; their rules!

Graem
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