How to Configure DKIM for a Custom Domain in Office 365

Enhancing Email Security with DKIM in Office 365

DomainKeys Identified Mail (DKIM) is a crucial email authentication protocol that helps verify the legitimacy of an email sender's domain, ensuring that email content remains unaltered during transit. By enabling DKIM in Office 365, organizations can significantly enhance their email security and improve deliverability. This article provides a detailed, step-by-step guide on setting up DKIM for custom domains in Office 365.

What is DKIM?

DKIM adds digital signatures to outgoing emails, allowing receiving servers to validate the message's origin and integrity. The process involves creating a private key associated with your domain name, which is then used to sign outgoing emails. The receiving mail servers use the public key published on DNS to verify these signatures, ensuring that the emails are genuine and not spoofed.

Step-by-Step Guide to Setting Up DKIM

Step 1: Create Office 365 DKIM Keys

1. Sign in to the Microsoft 365 Security Center:

- Navigate to the Microsoft 365 Security Center and sign in.

- Expand Email & Collaboration and click on Policies & Rules.

2. Access DKIM Settings:

- On the Policies & Rules page, select Threat Policies.

- Scroll down and under Rules, click on Email Authentication Settings.

- Click on DKIM and double-click on your custom domain (e.g., Cloudomega.site).

3. Generate DKIM Keys:

- Click on Create DKIM Keys to generate the signature keys.

- Copy the generated keys to a text editor like Notepad for later use.

Step 2: Add Office 365 DKIM CNAME Records to the Domain’s Registrar

1. Access Your Domain’s Registrar:

- Go to your domain registrar (e.g., Namecheap.com), and navigate to the advanced DNS settings.

2. Add CNAME Records:

- Add the two CNAME records copied from the Microsoft Security Center.

- Refresh the DNS settings page and return to the Microsoft 365 Security Center.

3. Enable DKIM:

- Enable DKIM for your Office 365 domain and click OK.

Step 3: DKIM Record Check

1. Verify DKIM Records:

- Visit [Mxtoolbox.com](https://mxtoolbox.com) and select DomainKeys Identified Mail under All Tools.

- Input your domain name (e.g., Cloudomega.site), use Selector1, and perform a DKIM Lookup.

2. Check Selector2:

- Perform the lookup for Selector2. If no DKIM record is found, return to the Microsoft Security Center and rotate the DKIM keys.

- Repeat the DKIM lookup on Mxtoolbox after rotating the keys.

Step 4: Verify with Message Header Analyzer

1. Send a Test Email:

- Send an email from your Office 365 mailbox to an external address.

2. Analyze Email Headers:

- In Outlook, view the message details by clicking the three dots and selecting View Message Details.

- Copy the message details and visit [mha.azurewebsites.net](https://mha.azurewebsites.net).

- Paste the message details into the analyzer and click Analyze Header. A successful configuration will show DKIM=pass.

By following these steps, you can ensure that DKIM is correctly configured for your custom domain in Office 365, enhancing your email security and improving deliverability.

Conclusion

Configuring DKIM is an essential step in securing your organization's email communication. It helps prevent email spoofing and ensures the integrity of your emails, thereby fostering trust with recipients. By following this guide, Office 365 users can efficiently set up DKIM for their custom domains.

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