Emails sent to external contacts being recieved and bouncing back

Question

At many of our M365 tenants we have setup our techsupport email techsupport@ourdomain as an external contact. Email sent to the M365 global admin admin@clientdomain ( our credentials) are forwarded to our techsupport email address.

Some months back Microsoft began forwarding emails to the Global admin admin@clientdomain with the email received by user@clientdomain as an attachment. The body of the email has the text “# Questionable URLs detected in message:” followed by the email’s header.

 

This has been going on for months and we have been receiving the forwarded emails at techsupport@ourdomain

 

Received a few such email today at techsupport@ourdomain but they were also bounced back to admin@clientdomain and we also received the bounce back at techsupport@ourdomain

 

Your message to IMCEAEX-_o=ExchangeLabs_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=******@namprd07.prod.outlook.com couldn't be delivered.

It further goes on to say “Your email program is using outdated address information for IMCEAEX-…

 

On checking the list of external contacts at tenant found that some external contacts were external_domainname.com#EXT#@clientdomain.onmicrosoft.com

And some as

external_domainname.com#EXT#@clientdomain.com

Our external contact was also setup as #EXT#@clientdomain.com

 

Our first assumption was that perhaps these are legacy contacts that came over in migration. Domain was migrated in 2103 , many new external contacts created  in 2021 were also setup as #EXT#@clientdomain.com

 

I sent an email from admin@clientdomain to our external contact & it was promptly received at techsupport@ourdomain.  Without bouncing back

 

This just started today , could it be some sort of bug that MS will fix or do I need to do something ?

 

Any thoughts ?

Answer 1

Hello Landsen,

The issue you're encountering seems to be related to email forwarding configurations and possibly some updated policies or settings within Microsoft 365. Here are several steps and considerations that may help in resolving or understanding this issue better:

1. Check Forwarding Rules:
   • Ensure that the forwarding rules set up in the Microsoft 365 admin center are correctly configured. You might need to revisit the rules and verify that they are set up to forward emails to techsupport@ourdomain as intended. The process to configure email forwarding is outlined in the Microsoft 365 admin documentation oai_citation:1,Configure email forwarding - Microsoft 365 admin | Microsoft Learn.
2. Review Organizational Policies:
   • Sometimes, organizational policies or settings might prevent emails from being automatically forwarded to external recipients. If this is the case, reconfiguring the rule that's blocking the forwarding might resolve the issue oai_citation:2,In MS O365 Auto forwarding mails bouncing back.
3. Check for Recent Updates:
   • Microsoft has updated the policy controls for users with automatic forwarding from on-premises email systems through Microsoft 365, as of an update mentioned in July 2023 oai_citation:3,Configuring and controlling external email forwarding in Microsoft 365 .... Check if there have been any recent updates or changes in Microsoft 365 that might affect email forwarding.
4. Investigate Bounce-Back Messages:
   • The bounce-back messages might provide clues on why the forwarding failed. Running a message trace in the Security & Compliance Center may provide additional details on the issue oai_citation:4,Email bounce back? - Microsoft Community Hub.
5. Check External Contacts Format:
   • Investigate the format of the external contacts in the tenant. As you mentioned, some contacts have a different format (external_domainname.com#EXT#@clientdomain.onmicrosoft.com vs. external_domainname.com#EXT#@clientdomain.com). Ensuring a consistent and correct format might help in resolving the issue.
6. Use Microsoft Support and Recovery Assistant:
   • Microsoft offers a Support and Recovery Assistant tool that can check for issues and help fix them. You might want to run this tool to check for any issues related to email forwarding oai_citation:5,Find and fix email delivery issues as a Microsoft 365 for business ....
7. Contact Microsoft Support:
   • If the issue persists, contacting Microsoft Support might provide more tailored assistance based on your specific setup and configurations.

The error message regarding outdated address information for IMCEAEX might indicate an issue with the recipient address format or a change in the addressing schema. It's advisable to review the configurations and possibly consult with Microsoft Support to gain a better understanding of the issue and how to resolve it. Please mark my answer if it was helpful :-)