Configuring DKIM for Trend Micro Hosted Email Security

Introduction to DKIM and Its Importance

DomainKeys Identified Mail (DKIM) is an essential email authentication method that ensures the legitimacy of outgoing emails. By adding a DKIM signature to email messages, Trend Micro Hosted Email Security (HES) helps prevent email spoofing and phishing attacks. DKIM allows the recipient's email server to verify that an email message was sent and authorized by the domain owner, ensuring that it has not been tampered with in transit.

Using DKIM along with SPF (Sender Policy Framework) and DMARC (Domain-based Message Authentication, Reporting, and Conformance) provides a comprehensive email security strategy, significantly reducing the risk of email fraud and ensuring high email deliverability rates.

How DKIM Works

DKIM uses a pair of cryptographic keys: a private key used by the sending server to sign outgoing emails and a public key published in the domain's DNS records. When an email is received, the recipient's email server fetches the DKIM public key from DNS and verifies the signature. If the signature is valid, it confirms that the email has not been altered and is indeed from the stated sender.

Configuring DKIM for Trend Micro Hosted Email Security

Step 1: Enable DKIM Signing for Your Domain

1. Access Outbound Protection:
   • Log in to the Trend Micro Hosted Email Security portal.
   • Navigate to Outbound Protection > DomainKeys Identified Mail (DKIM) Signing.
2. Add a New DKIM Signing Configuration:
   • Click on the Add button.
   • From the Domain Name drop-down menu, select the domain you want to configure DKIM for.
3. Configure DKIM Signing Options:
   • Select the DKIM Signing checkbox.
   • Configure the following settings:
     • SDID (Signature Domain Identifier): Choose the domain for which the DKIM signature will be applied.
     • Selector: Keep the default setting unless you have specific requirements for using multiple keys.
     • Headers to Sign: Choose which email headers should be signed to enhance security.
     • Wait Time: Specify the wait time before the key pair takes effect after being published in DNS.
4. Generate the DKIM Key Pair:
   • Click on Generate to create the DKIM public and private key pair.
   • Copy the generated public key as it will be needed for the next step.

Step 2: Publish the DKIM Record in DNS

1. Access Your DNS Management Interface:
2. Log in to your DNS provider’s management portal.
3. Navigate to the DNS settings for the domain you are configuring DKIM for.
4. Create a TXT Record for DKIM:
   • Name: s1._domainkey.yourdomainname.com
   • Type: TXT
   • Value: Paste the copied DKIM public key into this field.
5. Save the record and allow time for DNS propagation.

Step 3: Verify DKIM Configuration

After publishing the DKIM record in DNS, you should verify its correctness using various tools:

• Use a DKIM Checker or DKIM Lookup Tool.
• Enter your domain and selector (e.g., s1._domainkey.yourdomainname.com) to check if the DKIM record is correctly published.
• Use a DKIM Tester to Confirm Valid Signatures.
• Verify that the email passes DKIM validation.

Step 4: Enable DMARC for Additional Security

While DKIM helps authenticate emails, enabling DMARC further strengthens your email security by defining policies for email authentication failures.

Create a DMARC Record:

                Name: _dmarc.yourdomainname.com
                Type: TXT
                Value: v=DMARC1; p=quarantine; rua=mailto:[email protected]; ruf=mailto:[email protected]; sp=reject; adkim=s; aspf=s;
                    

Adjust the policy (p=none, p=quarantine, p=reject) as per your security preference.

Troubleshooting DKIM Issues

• Check DNS Propagation: It may take up to 48 hours for DNS changes to propagate.
• Validate TXT Record Formatting: Ensure there are no unnecessary spaces or incorrect characters in the DKIM record.
• Confirm Selector and Key Matching: The selector used in the DKIM check must match the selector configured in Trend Micro HES.
• Use a DKIM Generator: If needed, generate a new DKIM key pair and update the DNS record accordingly.

Conclusion

Implementing DKIM for Trend Micro Hosted Email Security is a crucial step in protecting your email domain from spoofing and phishing attacks. By following the steps outlined above, you can enable DKIM signing, publish the required DNS records, and verify the configuration using DKIM check tools. Additionally, integrating SPF, DMARC, and DKIM for Office 365 ensures a comprehensive email security setup.

For further verification, use DKIM Tester tools and regularly monitor your email authentication reports. Secure your domain today by configuring DKIM and enhancing your overall email security posture!