Steve Atkins via mailop skrev den 2024-10-21 16:28:
On 21 Oct 2024, at 14:33, Florian Effenberger via mailop
<mailop@mailop.org>
thanks to a friendly reader of this list, I tested the mail also with
aboutmy.email.
I can confirm now that when the Content-Encoding is 8bit, it gets
bounced by Mimecast, and also flagged as erroneus by aboutmy.email.
When I switch to Quote-Printable, the mail passes both just fine.
If you’re sending 8BITMIME payloads to aboutmy.email that’s probably
your problem. We don’t currently advertise 8BITMIME, and flag any
non-ascii character in the transaction as a problem.
8bitmime is ok in port 25, but it should be disabled in content filters
and signers, so its signed only as 7bit content
A lot of MXs advertise 8BITMIME, and many others will accept non-ascii
payloads even if they don’t, so violating it is a fairly common mistake
that doesn’t get noticed right away.
yes i have lost the howto link for how to make sure amavisd disables
8bit mime before it dkim sign its emails, try google it
But at that point you’re not sending email, so you’re outside the scope
of what DKIM promises to do.
if just maillist begin doing ARC-validate before mailman3 and friends
break dkim, it would not be so much disaster
its quite funny since all using rspamd where it all is supported, but
only a fail in mailflow so it see it all breaks
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