From postfix-users Sat Nov 23 09:26:02 2019 From: Dominic Raferd Date: Sat, 23 Nov 2019 09:26:02 +0000 To: postfix-users Subject: Re: Validation DMARC Message-Id: X-MARC-Message: https://marc.info/?l=postfix-users&m=157450125219563 MIME-Version: 1 Content-Type: multipart/mixed; boundary="--00000000000001fe9205980020d6" --00000000000001fe9205980020d6 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, 23 Nov 2019 at 09:14, Roland K=C3=B6bler wrote: > Hi, > > > when validating DMARC, it use the envelop address, or use from address > from the header? > it unfortunately uses the from-header. > (If it would use the envelope address, it would not cause that much > problems.) > > Or in short: DMARC intentionally breaks every mailinglist and every > mail-forwarding. > So, if a mail-provider uses a strict DMARC-policy, it effectively > says: "Our mail-addresses may not be used for mailinglists." > DMARC's focus on the From header is absolutely correct because it is about stopping forging. And it is simply untrue that DMARC breaks all mailing lists nor that it breaks all mail forwarding. I realise a lot of people on mailing lists about email have a downer on DMARC because depending on (a) the implementation of DKIM by the sender's domain controller and (b) on the setup of the mailing list it can - but often doesn't - cause problems. But it is a very powerful tool for preventing forging of emails. Domain controllers who are not bothered about forging of emails from their domain are not obliged to use it. --00000000000001fe9205980020d6 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Sat, 23 Nov 2019 at 09:14, Roland K=C3=B6bler &l= t;rk-list@simple-is-better.= org> wrote:
Hi,

> when validating DMARC, it use the envelop address, or use from address= from the header?
it unfortunately uses the from-header.
(If it would use the envelope address, it would not cause that much
problems.)

Or in short: DMARC intentionally breaks every mailinglist and every mail-fo= rwarding.
So, if a mail-provider uses a strict DMARC-policy, it effectively
says: "Our mail-addresses may not be used for mailinglists."
<= /blockquote>

DMARC's focus on the From header is absolutely correct because i= t is about stopping forging. And it is simply untrue that DMARC breaks all = mailing lists nor that it breaks all mail forwarding.

I realise a lot of people on mailing lists abo= ut email have a downer on DMARC because depending on (a) the implementation= of DKIM by the sender's domain controller and (b) on the setup of the = mailing list it can - but often doesn't - cause problems. But it is a v= ery powerful tool for preventing forging of emails. Domain controllers who = are not bothered about forging of emails from their domain are not obliged = to use it.
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