Someone else mentioned the encoded issue and that is the first thing to check. Are there any non-ASCII characters in the message anywhere, but particularly in the headers? And if you’re sending from Google then there isn’t much you can do about it.
I wanted to talk about the broader pattern here. This is a regular failure mode at Microsoft that a number of people in the deliverability space have been tracking for a few months now. We’re not sure what’s happening, it’s difficult to reproduce. We have seen that the messages that fail will often be accepted on a second attempt. I’ve also seen SPF=fail, DKIM=Pass, DMARC=pass in the rejections as well. We’ve seen most of the rejections from some machine clusters and none from other clusters. I’ve been slammed the last few weeks and haven’t looked at this for a while, and need to add some new data to the writeup I’m working on so I may have forgotten some details. But this has been going on for a while and we’re not sure how to mitigate it. There’s nothing obvious about why the mail is failing and, in fact, the same message redelivers fine to Microsoft. Unfortunately, it is something only MS can fix. They’ve been alerted, they are aware of the issue and there was some talk in Barcelona last month that MS had said they were expecting to roll out a fix by the end of April. It appears they might have missed their ship date. laura > On 6 May 2026, at 07:57, Hello Maildrop via mailop <[email protected]> wrote: > > Hello, > > One of my customer, hosted at Google workspace, have recurrent problem when > sending to some addresses at live.fr <http://live.fr/> or hotmail.com > <http://hotmail.com/> > > The messages bounce back indicating a DKIM failure, however the messages > sended are well signed. Delivery to other destinations enforcing DKIM/DMARC > does not cause any problems (Gmail, Orange) > > 550 5.7.515 Access denied, sending domain MISSEGLE.COM <http://missegle.com/> > doesn't meet the required authentication level. The sender's domain in the > 5322.From address doesn't meet the authentication requirements defined for > the sender. To learn how to fix this see: > https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , > DMARC= Pass [AM8P189MB1234.EURP189.PROD.OUTLOOK.COM > <http://am8p189mb1234.eurp189.prod.outlook.com/> 2026-05-06T05:21:48.296Z > 08DEAAD6427386FD] [DU2PR04CA0024.eurprd04.prod.outlook.com > <http://du2pr04ca0024.eurprd04.prod.outlook.com/> 2026-05-06T05:21:48.305Z > 08DEAAEBE699717D] [DB1PEPF000509FE.eurprd03.prod.outlook.com > <http://db1pepf000509fe.eurprd03.prod.outlook.com/> 2026-05-06T05:21:48.308Z > 08DEA716CB8BDD0A] > > I can't identify the cause of this problem, do you have any ideas? > TOUREL David > > > > MAILDROP > 17 ch de la Longuié - 81210 MONTFA > > Tél : 05 63 51 07 79 > > Retrouvez-nous sur Twitter @maildrop_fr > <https://twitter.com/maildrop_fr>_______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop -- The Delivery Expert Laura Atkins Word to the Wise [email protected] Delivery hints and commentary: http://www.wordtothewise.com/blog
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