I've had a bounce from a mimecast hosted domain that I don't understand, and should be grateful for any help. I'm redacting localparts, but nothing else.
The message is sent From: [email protected], to a private mailing list [email protected] . That list simply distributes the incoming message to the members, using a MailFrom of [email protected], and otherwise leaving all headers unchanged apart from Return-Path, Received, and a private X-SB-DKIM-Status header. The relevant incoming message has a valid btinternet.com DKIM signature DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=btmx2012311; t=1725539173; bh=urOLPb3Q/X5gx8ga5bbc2Wtt2iVG68mriPcqcbSGWKc=; h=From:Mime-Version:Date:Subject:Message-Id:To:X-Mailer; b=Wi/V5iktJPJtYQDx2bUaDokVYUsD++5KTZxp7+6NMZ7osfN6S9VkjstJ/6djJRaeYfmRHdVK2SwGIgVuhD/xzP8qQm1K9Vn9ARZL88kpalceLsm3A9/836IS3Gd8DOJEKAIY3C6mBwovXcGovtS1v1gV6Iza975s9NqxAkKaCEP3eNDfQTNo8MT+qVB33/RhnXdrC2SQxcmdgZr0ApvhW60yDHUS8eAKWdglYk/+h34it1mdYCYagrsETsdtOeEW4VDjoTuL5AGNtpgAJk/H89hz6EG85+EtV/tKF4nTH2hsD02cCDl03BNkaLwowniWSCjuUOTrCgdXnnvK7R/8YA== One of the recipients is [email protected], and that delivery results in a bounce: [email protected] (generated from [email protected]) host eu-smtp-inbound-2.mimecast.com [195.130.217.241] SMTP error from remote mail server after end of data: 550 DMARC Sender Invalid - envelope rejected - https://community.mimecast.com/docs/DOC-1369#550 [Mx-vWL2qP5eCQ7y2fByS5w.uk156] The help reference says that this means the SPF check in DMARC fails. Well, of course it does, because the MailFrom is no longer the From:. In fact, vanilla SPF passes, but the envelope is not aligned, so it's not relevant for DMARC. However, DKIM passes, as verified on the incoming message by my server, so DMARC should pass. What am I missing? Thanks for any enlightenment! Julian. _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
