I have a number of Exchange Online mailboxes set to forward to different Gmail and Outlook.com addresses via mail flow configuration.
From Monday (08/10/2018), all forwarded mail from firstname.lastname@example.org (the default from-address of SharePoint Online used for alerts and workflow email) has ended up in the spam/junk folder of the recipient account.
It appears that the forwarded mails are failing DMARC so are being quarantined by the recipient mailbox.
Authentication-Results: spf=pass (sender IP is 184.108.40.206)
smtp.mailfrom=mytenant.onmicrosoft.com; outlook.com; dkim=pass (signature was
verified) header.d=mytenant.onmicrosoft.com;outlook.com; dmarc=fail
Received-SPF: Pass (protection.outlook.com: domain of mytenant.onmicrosoft.com
designates 220.127.116.11 as permitted sender)
The way I understand it, DKIM and SPF are passing but DMARC is failing because theheader.d address does not match theheader.fromaddress.
Is that about right? Is there any way around this?
I understand that I need to add a DKIM record for sharepointonline.com to my domain but I'm just using the default mytenant.onmicrosoft domain. I'm not using a custom domain. Surely Microsoft should have configured this already?