Hi again,
Good point about DMARC. Does anyone know if Charter suddenly started
caring about some DMARC policies on or around this past Friday? I have
my list set to munge the From: lines of messages from senders E.G. AOL,
Yahoo, etc. that publish a DMARC rejection policy.
On a slightly different topic, I've heard from a few Outlook users that
list messages are consistently ending up in their junkmail folders.
Could this be because Microsoft doesn't like the fact that my list is
causing DMARC to fail, but not actually complaining to me about it? I
could solve this problem by having the list munge the From: line for all
messages, but sometimes that causes problems with replying. In
particular, several years ago when my lists were set up to do that,
Thunderbird users were having problems sometimes replying to the sender
of a message rather than the entire list.
Jayson
On 11/28/2021 11:45 PM, Mark Sapiro wrote:
On 11/28/21 7:58 PM, Jayson Smith wrote:
Hi,
One of my Mailman lists has a single member at Charter which has
occasionally bounced mail over the last few days. When this happens,
the reason given, when I look it up on their help page, indicates the
message I sent goes against the security policies of my domain, and I
should contact my domain administrator (that would be me). I have SPF
and DKIM set up, and a quick check at dkimvalidator.com verifies
they're both working. I assume this is one of these annoying
situations where Charter is seeing what's clearly a transient DNS
problem and treating it like a permanent failure? Also I assume
there's nothing I can do about this? Is the problem likely to be at
Charter's end or at my domain's nameservers' end?
Only guessing, but this sounds like DMARC. Does your list apply DMARC
mitigations?
If it is DMARC, the issue is the message sent to the charter
subscriber is From: poster@posters.domain. posters.domain publishes a
DMARC policy of (probably) reject. Yahoo.com is one such common
domain. Your list modifies the message by content filtering, subject
prefixing, adding msg_footer or some other transformation that breaks
the posters.domain DKIM signature. Your SPF and DKIM signatures pass,
but they are not 'aligned' with posters.domain, so they don't count
for DMARC.
See https://wiki.list.org/DEV/DMARC
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