[Mailman-Users] cause of bounces

Mark Sapiro mark at msapiro.net
Wed Oct 18 14:35:04 EDT 2017

On 10/18/2017 11:14 AM, Grant Taylor via Mailman-Users wrote:
> I think it will be interesting to see what happens as more and more
> domains adopt DMARC, including those that use p=reject.  Especially with
> some of governmental institutions purportedly being mandated to use
> DMARC.  -  IMHO, DMARC is going to eventually become the new norm.

DMARC is not the problem. It is perfectly reasonable for say, irs.gov to
publish DMARC p=reject as long  as mail From: irs.gov is not an
employees personal post to an email list. Presumably the IRS would have
rules against that.

The problem is when general ESPs that provide addresses in their domain
for anyone to use for any personal purpose publish DMARC p=reject.

> I also wonder what ARC is going to do to this paradigm.

ARC has the potential to help. When say a yahoo.com user posts to a list
on my server and the list sends the post to a hotmail.com user, ARC
allows me to certify that Yahoo's DKIM signature was valid when I
received the mail, then I broke the sig but resigned the mail with my
domain's sig and sent it on to Hotmail. Now there is a chain by which
Hotmail can verify my sig and the fact that I certify Yahoo's sig. The
crux however is Hotmail has to trust me. Now if I'm GoogleGroups,
Hotmail will probably trust me but if I'm mail.python.org there might be
a mechanism by which I can ask Hotmail and every other ISP to trust me,
but is that going to work in practice. I think that remains to be seen.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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