How to Handle Microsoft’s Quiet DKIM Value Settings Update for Email Signing in Office 365?

Why Did Microsoft Change DKIM Settings in Office 365 Without Warning?

Microsoft recently made a change to the DKIM (DomainKeys Identified Mail) value used for signing emails in Office 365. This adjustment happened with little to no prior notification, leaving many administrators scrambling to catch up. Let’s break it down and explain what this means for your organization.

DKIM is like a digital signature for your emails. It helps verify that an email is actually from your organization and hasn’t been tampered with during delivery. Without proper DKIM setup, your domain could be vulnerable to:

• Spoofing: Attackers pretending to send emails from your domain.
• Phishing: Fraudulent emails targeting your users or customers.
• BEC (Business Email Compromise): Scams that trick employees into transferring money or sharing sensitive data.

In short, DKIM is critical for email security and protecting your business reputation.

What Changed?

• Microsoft adjusted the CNAME value used for DKIM in Office 365.
• This change wasn’t widely communicated, leaving some admins unaware of the update.
• Some users report seeing outdated CNAME entries in the admin center, adding confusion.

How to Address This Issue

Here’s how you can ensure your DKIM setup is correct and up-to-date:

Step 1: Check Microsoft’s Official Documentation

1. Visit the support article titled Setting up DKIM to sign emails from your Microsoft 365 domain.
2. Review the section on CNAME syntax carefully.

Step 2: Verify Your Current CNAME Entries

1. Log into the Microsoft 365 admin center.
2. Navigate to the DNS settings for your domain and compare them with the updated values in Microsoft’s documentation.

Step 3: Update Your DNS Records If Necessary

Replace any outdated CNAME entries with the new values provided by Microsoft.

Step 4: Test Your Configuration

Use tools like MXToolbox to confirm that DKIM is working as expected.

Step 5: Monitor for Future Changes

Subscribe to Microsoft’s update channels or newsletters to stay informed about changes like this in the future.

Why This Matters for Administrators

This quiet update could leave your organization exposed if not addressed promptly. Outdated DKIM settings might fail to authenticate emails, increasing the risk of phishing or spoofing attacks targeting your domain.

Microsoft’s lack of communication here is frustrating, but fixing this issue is straightforward if you act now. Regularly reviewing your email authentication settings can save you from bigger headaches later on.