A customer called and told me about missing planner mail notifications. It was very strength, because the most notifications arrived the users. Only in some cases the users didn’t get a mail from planner.
After a while we found some facts:
- round about 8/10 notifications arrived the recipient
- all plans where created directly in planner
- no problems with other notifications
- Exchange Hybrid is configured
The fist step to troubleshoot, I created a Plan from Planner and a Microsoft Teams (with an plan) from the Teams Client.
Ok, it was not the best name choise 😉
After I had create the group I took a detail look with the Graph Explorer. In the Graph Explorer I saw a difference between the to groups. Only the group, I had created from Microsoft Teams, had a SMTP option. The Plan I created directly from Planner had no SMTP entry.
After a short search I founded a blog post from Vasil Michev
[…] Tony Redmond’s educated guess was that the new address has something to do with the switch to using EWS for sending any SharePoint related notifications. Later on, this has been half-confirmed by Microsoft, by referring us to the following KB article. Unfortunately, this article is a bit short on details on what exactly the address is needed for, as EWS impersonation can simply work with a regular SMTP address. Maybe it’s deliberately chosen so it doesn’t interfere with the ‘regular’ SMTP addresses, as this method is also used for impersonating users without mailboxes (however that should work). In any case, details are scarce at this point, and the above article is all we have – take it or leave it […]https://www.michev.info/Blog/Post/1412/new-type-of-addresses-in-office-365-spo
If we go in the details we find the reason:
For example, before this change a user named Alice, who doesn’t have an Exchange Online mailbox shares a file in SharePoint with Bob. Because Alice doesn’t have an Exchange Online mailbox, we would send the message from the SharePoint Simple Mail Transfer Protocol (SMTP) servers, and then spoof the From field of the message to have the name and email address of Alice. If the spoofed message has conflicts with spam filters, the message is delivered to the Junk Email folder or rejected completely. In the past, we advised you to include the SPF records for “sharepointonline.com” in your SPF records as a mitigation for this problem. The change to SharePoint will no longer spoof the email address for such messages.https://support.microsoft.com/en-us/office/information-about-changes-to-the-address-that-is-used-to-send-notification-email-messages-from-sharepoint-ae01f2a0-acca-499b-ab96-df0e996d367a?ui=en-us&rs=en-us&ad=us
My recommendation: Create a Microsoft Teams and from there create a new planner plan.