On 2022-05-09, Slavko via Exim-users <exim-users@???> wrote: > Dňa 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!
