At 13:25 02/03/2018 -0700, Thomas Morley wrote:
Paolo Prete wrote
For unknown reasons I don't see your posts on the mailing-list, ...
Neither do I. But I can help there: it's all down to Domain-based
Message Authentication, Reporting and Conformance (DMARC). This is a
comparatively new system whereby mail domains can publish information
to confirm or otherwise that messages are genuinely sent from a mail
server maintained by that domain. Paolo Prete's mail domain appears
to be yahoo.it, and Yahoo is one of the sending domains that uses
this system. If he sent to you directly, everything would work OK and
Gmail would accept the message.
The problem arises with mailing lists. The server forwarding the
message - in this case Lilypond's - is not a proper source for
@yahoo.it messages, of course, so Gmail quite properly rejects list
messages claiming to be from Yahoo addresses as spoofed. (As it
happens, so does my mail provider.) If it is configured properly,
mailing list software can arrange headers so that the receiving
system - Gmail's in your case - sees his Yahoo server as the
originator instead of the mailing list's. The problem is that most
list software available when this protection was introduced was
incapable of being properly configured. To avoid this effect,
Lilypond may need to update the list software (apparently Mailman
2.1.21) or maybe just configure it differently.
https://en.wikipedia.org/wiki/DMARC - which includes "In April 2014,
Yahoo changed its DMARC policy to p=reject, thereby causing
misbehavior in several mailing lists."
https://wiki.list.org/DEV/DMARC for details of Mailman's behaviour.
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