For years, I've been using outlook with some mails @netcabo.pt. Since this morning, keeping receiving mails sent to me, my own mails are blocked.

Hi @ANIMANOSTRA CAM LDA, 

Thank you for reaching out to Microsoft Q&A Forum. 

After conducting some research and testing the setup steps in a virtual environment, I’d like to share a few recommendations that may help resolve the DKIM issue you've encountered. I understand how frustrating these authentication errors can be, and I’m here to support you through it. 

Based on the error message, it seems DKIM is currently failing, while SPF and DMARC are passing. I understand this can be confusing in most cases, this simply means DKIM hasn’t been fully enabled yet, or the required DNS records haven’t been correctly published or had time to propagate. Here’s a quick checklist to help you fix this: 

Step 1: Check DKIM Status in Microsoft 365 Admin Center 

• Open your browser and go to: https://admin.microsoft.com
• Sign in using your Microsoft 365 admin account. 
• In the left-hand menu, select “Security”  
• Go to “Email & collaboration” > “Policies & rules” > “Threat policies”. 
• Under “Email authentication settings”, select “DKIM”. 
• Locate the domain netcabo.pt in the list. 

Please check the “Status” and “Toggle” fields in the DKIM configuration panel.  If the status shows “CnameMissing” or “No DKIM keys”, it means the DKIM setup has not been completed or the DNS records have not yet propagated.  In this case, you will not be able to enable DKIM for the domain until the required CNAME records are correctly published and recognized.   

Step 2: Create or Update DKIM DNS Records 

1. Locate the domain netcabo.pt in the list. 
2. Choose the domain you want to configure DKIM for (e.g., NETCABO.PT). 
3. Microsoft will display two CNAME records that need to be published in your domain’s DNS. 

• Log in to your domain registrar or DNS hosting provider  
• Go to DNS management. 
• Add the two CNAME records exactly as shown. 
• Save the changes. 

Step 3: Enable DKIM in Microsoft 365 

Once the DNS records have been added and successfully propagated: 

1. Go back to the DKIM configuration page in the Microsoft 365 Admin Center. 
2. After the CNAME records are correctly resolved or updated, the Status will show “Valid”. 
3. At that point, you can simply toggle the switch from “Disabled” to “Enabled” to activate DKIM for your domain. 

Note: Check if the domain in the DKIM signature (d=) matches the domain in the “From” address (5322.From). This is important because for DMARC to work properly, the domain used to sign the email (DKIM) must align with the domain that appears in the sender’s address. If they don’t match, DMARC may fail even if DKIM passes technically. 

Please wait 15 minutes to 24 hours for DKIM to complete configuration. Then double-check by sending a test email and check if DKIM shows as pass in the message headers. Also, avoid using overly promotional content or spam-like keywords in your emails to prevent delivery issues.

If you still experience problems sending emails, please take a screenshot of the error or bounce message and send it to me. I’ll support you further.

If I’ve misunderstood anything or if any part of this explanation isn’t clear, please don’t hesitate to let me know. I truly want to make sure this works smoothly for you, and I’m here to help however I can. 

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