On 05/09/2024 14:53, Julian Bradfield via mailop wrote:
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 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.
I had a problem a couple of years ago with Mimecast marking some DKIM-signed emails as failing, even though they passed everywhere else.
After escalating the ticket several times and with a lot of insistence from us, Mimecast eventually admitted that "the cause of the issue is our limited support for 8bit encoding".
At the time they said that "no ETA has been shared with us but the engineering case has been open for quite some time".
I don't know if it ever got fixed, as we worked around it. Maybe that could be the same issue?
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