Hello @carter fridd,
Thank you for posting your valuable question on Microsoft Q&A forum.
According to your description, here is a breakdown of possible causes and solutions for your issue:
Domain Not Verified in Microsoft 365
If the domain isn’t verified, Microsoft won’t route emails to it. You can:
- Log into the Microsoft 365 Admin Center.
- Navigate to Settings > Domains.
- Follow the steps to verify your domain (usually involves adding a TXT record).
DNS Records Not Set Up Correctly
Missing or incorrect MX (Mail Exchange) records can prevent email delivery.
- Go to your domain registrar (e.g., GoDaddy, Namecheap).
- Ensure the MX records match those provided by Microsoft 365.
- You may also need to set up SPF, DKIM, and DMARC records for email authentication.
DNS changes can take time to propagate. Please wait up to 24–48 hours after making DNS changes.
For your reference: Add DNS records to connect your domain - Microsoft 365 admin
Mailbox Not Properly Created or Assigned
The custom email address may not be linked to an active mailbox.
- In the Admin Center, go to Users > Active Users.
- Ensure the email address is assigned to a user with a mailbox.
- If not, create a mailbox or assign the email to an existing user.
Run a message trace
You can check a status of the missing email whether it was delivered, delayed, or failed and the reasons for delivery failure, if applicable:
- Go to the Microsoft 365 Defender portal
Sign in with your admin credentials. - In the left-hand navigation, go to: Email & Collaboration > Review > Message Trace
- Choose the date range and enter the email address you want to trace (e.g., your custom domain email).
- Click Search to view the trace results.
Please understand that our initial response does not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.
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