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