To second what others have said, header noncompliance can indeed manifest as DKIM failures at Microsoft.
Example number one -- double headers: https://www.engagor.ai/resources/blog/duplicate-headers-dkim-microsoft-bounce Example number two -- too long header: https://postmarkapp.com/blog/how-we-improved-unsubscribe-links-to-boost-your-deliverability Cheers, Al Iverson On Wed, May 6, 2026 at 8:45 AM Paulo Azevedo via mailop <[email protected]> wrote: > > Hi all. > > I had a similar issue with a customer: turned out that the "script" > generating the email message wasn't adding a Message-ID header. > Had the server add the missing header before dkim signing, issue solved. > > Sometimes the devil is on the details ... > > > On Wed, May 6, 2026 at 12:26 PM Jonathan Loriaux via mailop > <[email protected]> wrote: >> >> Hi David, >> >> To properly identify the problem, you need to analyze the SMTP headers of a >> successfully delivered email (to a different destination, for example). >> >> Feel free to contact me privately if you need help. >> >> Jonathan >> >> P.s. : N'hésitez pas à vous inscrire à nos newsletters : >> https://www.badsender.com/newsletter/inscription/ >> >> -- >> Jonathan Loriaux >> >> CRM Consultant and >> Co-director of Badsender >> >> 07.62.33.33.47 >> >> [email protected] >> >> badsender.com >> >> lepatron.email >> >> Facebook Twitter Linkedin >> >> Book a meeting with me >> >> >> >> >> >> On 5/6/26 08:57, Hello Maildrop via mailop wrote: >> >> Hello, >> >> One of my customer, hosted at Google workspace, have recurrent problem when >> sending to some addresses at live.fr or 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 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 >> 2026-05-06T05:21:48.296Z 08DEAAD6427386FD] >> [DU2PR04CA0024.eurprd04.prod.outlook.com 2026-05-06T05:21:48.305Z >> 08DEAAEBE699717D] [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 >> >> _______________________________________________ >> mailop mailing list >> [email protected] >> https://list.mailop.org/listinfo/mailop >> >> _______________________________________________ >> mailop mailing list >> [email protected] >> https://list.mailop.org/listinfo/mailop > > > > -- > -- > Paulo Azevedo > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop -- Al Iverson // 312-725-0130 // Chicago http://www.spamresource.com // Deliverability http://www.aliverson.com // All about me https://xnnd.com/calendar // Book my calendar _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
