Securing Email Delivery with DKIM for Microsoft 365

In today’s business environment, securing email delivery is essential. Email remains the primary form of communication for most businesses, and ensuring its reliability and security is critical to maintaining the trust of your customers, colleagues, and partners. One of the key tools for achieving this is DKIM (DomainKeys Identified Mail), which adds an essential layer of protection for your outbound email traffic.

What is DKIM?

DKIM is a method of email authentication that uses a digital signature to verify that an email was sent and authorized by the owner of a specific domain. It ensures that the email’s content hasn’t been altered in transit and helps prevent spoofing and phishing attacks. Essentially, it’s like stamping your emails with a verified seal of approval.

Here’s how it works:

• DKIM signs all outbound emails at the last hop or edge of your mail service using a private key.
• The recipient’s mail server uses the corresponding public key, published in your DNS records, to verify the authenticity of the email.

Why is DKIM Important?

Implementing DKIM offers several critical benefits for your organization:

• Improved Email Deliverability: Emails signed with DKIM are more likely to reach your recipients’ inboxes instead of being flagged as spam.
• Enhanced Email Security: By verifying the authenticity of the sender, DKIM reduces the risk of email spoofing and phishing attacks.
• Domain Reputation Management: Consistent DKIM authentication helps maintain a positive domain reputation, which is vital for email deliverability.
• Brand Protection: DKIM prevents unauthorized use of your domain for sending emails, safeguarding your business reputation.

Key Consideration: Setting Up DKIM at the Right Location

When implementing DKIM, it’s critical to configure it at the final exit point of your mail system. For example, if you use a third-party service like Mimecast to scan all outbound emails, the DKIM setup should be done within Mimecast. This ensures that all outbound emails are properly signed before being sent to recipients.

How to Set Up DKIM with Microsoft 365

Follow this step-by-step guide to configure DKIM for a domain in Microsoft 365:

1. Access the Admin Center
   • Navigate to admin.microsoft.com.
2. Expand Settings
   • In the left-hand menu, expand the Settings section.

3. Select Domains
   • Click on Domains and select the domain you want to configure DKIM for.

4. Manage DNS Records
   • Click on DNS Records and then Manage DNS.

4. If prompted with “How do you want to connect your domain?”, choose your preferred option. For manual control, select “Add your own DNS records.”

5. Enable DKIM
   • Under advanced options, check the box for DomainKeys Identified Mail (DKIM).

6. Retrieve DNS Records
   • Microsoft will provide the required DNS records. Copy these records for the next step.

7. Update Your DNS Provider
   • Identify your DNS provider. If unsure, use tools like Google’s Dig tool to find your domain’s nameservers.
   • Log in to your DNS provider’s portal (e.g., Cloudflare, GoDaddy).
   • Add the DNS records supplied by Microsoft. For reliability, I recommend Cloudflare due to its performance, security, and service offerings.
8. Wait for DNS Propagation
   • DNS changes can take up to 48 hours to propagate, though many providers update records instantly. For verification, use tools like Google’s Dig tool.
9. Verify and Finalize DKIM in Microsoft 365
   • Once the DNS records are live, return to the Microsoft 365 Admin Center.
   • Click Continue and verify that the setup is complete.

9. Click Done to finish the process.

Do not forget! You also need DMARC configured to fully benefit from DKIM, check my other post: Why You Need DKIM and DMARC to Protect Your Business

Fantastique, vous disposez maintenant de la configuration DKIM.