Hello Charlie Toon,
Good day!
Thank you for your question and for being a part of our community!
I understand that you are experiencing an ‘unverified sender’ message in Outlook (both desktop and web app) despite adding the address to the ‘trusted sender’ and whitelisting the domain. This can be frustrating, especially when the sender is trusted and from a reputable domain.
I see that you have already tried adding the address to the ‘trusted sender’ list and whitelisting the domain. These are indeed the correct initial steps to take.
Despite these steps, the ‘unverified sender’ message can still appear if the sender’s domain lacks proper email authentication methods like SPF, DKIM, and DMARC. These protocols help verify the sender’s identity and ensure the email is not spoofed.
Kindly verify that the sender’s domain has proper SPF, DKIM, and DMARC records set up. This is crucial for email verification and can help prevent the ‘unverified sender’ message. How to use DKIM for email in your custom domain - Microsoft Defender for Office 365 | Microsoft Learn, Use DMARC to validate email, setup steps - Microsoft Defender for Office 365 | Microsoft Learn and Set up SPF identify valid email sources for your Microsoft 365 domain - Microsoft Defender for Office 365 | Microsoft Learn.
I strongly recommend that you open a service request, the technical support there has more resources and permission than we do here in the community and then can collect the logs to investigate this issue from the back end and they can also go on remote sessions with you to navigate your set up Get support - Microsoft 365 admin | Microsoft Learn. This will be the most efficient way of handling your issue. I want to assure you that I'll be tracking this issue and doing follow-ups to ensure it gets resolved once and for all after you have opened a service request.
Kindly have this information before opening a service request:
- What version of Outlook do you have? What version of Outlook do I have? - Microsoft Support
- Have you noticed this issue with multiple senders or just one specific sender?
- Is the sender’s domain using proper email authentication methods like SPF, DKIM, and DMARC?
Kindly take note of having the necessary information that was asked to narrow down your issue to help our support team handle your issue more efficiently. Also, let them know the steps you have taken previously to troubleshoot the issue so they know how to go about it and investigate further.
Thank you for your time and understanding. For other questions, feel free to add your post to the Microsoft Community.
Sincerely,
Eleni | Microsoft Community Moderator.