On 21 Sep 2026, at 10:54, Jörg Backschues via mailop wrote: > Am 21.09.26 um 09:51 schrieb Sebastian Hagedorn via mailop: > >> our help desk has notified me that mails from our SIEVE-based vacation >> autoresponder aren’t accepted by Microsoft anymore. Microsoft complains >> about the From address: >> >> "The sender's domain in the 5322.From address doesn't meet the >> authentication requirements defined for the sender" >> >> I am guessing that refers to the envelope From, which is <> – as it should >> be according to RFC 5230. The header From is using our domain, the outgoing >> messages are DKIM-signed, and we have a DMARC policy. Regular messages are >> accepted by Microsoft, so my best guess is that the empty envelope From is >> causing the problem. Is anybody else seeing this? I don’t see how we can do >> anything about that on our end. > > Your SPF "HELO" identity ist missing > > kdig txt mail-out-v1.uni-koeln.de > > RFC 7028 Sec. 2.4 > "[RFC5321] allows the reverse-path to be null (see Section 4.5.5 in > RFC5321]). In this case, there is no explicit sender mailbox, and > such a message can be assumed to be a notification message from the > mail system itself. When the reverse-path is null, this document > defines the "MAIL FROM" identity to be the mailbox composed of the > local-part "postmaster" and the "HELO" identity (which might or might > not have been checked separately before)." > > e.g. > > kdig txt mail-out-v1.uni-koeln.de. > > mail-out-v1.uni-koeln.de TXT "v=spf1 ip4:134.95.86.58 ip6:2a00:a200:0:13::58 > -all"
Thanks, I wasn’t aware of that. I have now added the pertinent records. For the
archive, it’s RFC 7208, not RFC 7028.
Cheers,
Sebastian
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