When I ran into those messages in the past from Google, the messages actually did not have multiple from addresses. It turns out the issue was the friendly from part had certain special characters in it. Not all special characters, but certain ones do trigger this bounce mesage.
So check that first before digging any deeper. I went down this rabit hole ;-) Kind Regards, Richelo Killian From: Alessandro Vesely via mailop <mailop@mailop.org> <mailop@mailop.org> Reply: Alessandro Vesely <ves...@tana.it> <ves...@tana.it> Date: December 14, 2021 at 09:55:41 To: mailop@mailop.org <mailop@mailop.org> <mailop@mailop.org> Subject: Re: [mailop] Gmail rejects multiple From:'s. Who else? On Mon 13/Dec/2021 18:51:48 +0100 Brandon Long wrote: > On Mon, Dec 13, 2021 at 9:46 AM Slavko via mailop <mailop@mailop.org> wrote: >> Dňa Mon, 13 Dec 2021 18:19:07 +0100 Alessandro Vesely via mailop < mailop@mailop.org> napísal: >> >>> Is it customary to reject messages with multiple addresses in From:? >>> Why? >> >> AFAIK, DMARC works with only one From: address, thus sites which >> are verifying DMARC tends to reject multiple addresses in it. > > Basically, yes, DMARC doesn't handle multiple from addresses, otherwise one > could do From: m...@whatever.com, accou...@google.com and which domain would > this be considered from? I guess one could evaluate DMARC for both. Evaluating both doesn't make much sense, because a DMARC receiver is actually verifying proper sending from the author's domain. The author who added one or more coauthors in the From: line is still sending through her usual MUA and submission server. Thus that's the only domain which is worth verifying. A Sender: line should point to the right domain. However, I'd propose that the sender be the first address in the From: line, which grants visibility and simplifies verifiers' code. > We also reject multiple From headers, which is much more common but > basically always an error or spam. Yes, that's explicitly forbidden and a known DKIM vulnerability (DKIM signers should specify From: twice in h=). Best Ale -- _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
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