How to Set Up DKIM for Mailgun

Mailgun is a powerful transactional email service used by developers and businesses. Proper DKIM configuration ensures your emails are authenticated and delivered reliably.

Why Set Up DKIM in Mailgun

Without DKIM:

• Emails may be flagged by spam filters
• Deliverability suffers, especially at scale
• Recipients' email servers can't verify authenticity

With DKIM:

• Emails are cryptographically signed
• Better inbox placement
• Improved sender reputation
• Compliance with email authentication requirements

Before You Start

You'll need:

• A Mailgun account
• Access to your domain's DNS settings
• The domain you want to send from

Step-by-Step Setup

Verify Your Setup

After Mailgun verifies your domain, test the DKIM record publicly.

Common Mailgun selectors:

• smtp._domainkey.yourdomain.com
• mailo._domainkey.yourdomain.com

Check what Mailgun provided during setup—selectors may vary.

Mailgun DKIM Record Format

Mailgun typically uses a TXT record format:

k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ...

Note that Mailgun's format doesn't always include v=DKIM1; at the beginning—this is valid, as the version tag is optional.

Common Issues and Solutions

"Unverified" status

Cause: DNS records not found or incorrect.

Solutions:

• Wait for DNS propagation (15-30 minutes typical)
• Double-check the record values match exactly what Mailgun provided
• Ensure you added TXT records, not CNAME records (for DKIM)
• Verify there are no extra spaces or truncation in the value

Record shows "hostname" in Mailgun

Cause: The DKIM record name may need adjustment.

Solution: Some DNS providers want just the subdomain (smtp._domainkey), others want the full name. Try the format your provider expects.

Emails sent but DKIM fails

Cause: Possible mismatch between sending domain and DKIM domain.

Solutions:

• Ensure you're sending from the verified domain
• Check that your code specifies the correct "From" domain
• Verify the domain in your Mailgun API calls matches the verified domain

Mailgun + Common Integrations

WordPress + Mailgun

When using the Mailgun WordPress plugin:

1. Set up DKIM in Mailgun first
2. Configure the plugin with your Mailgun API key
3. Set the "From" address to use your verified domain

Laravel + Mailgun

In your .env:

MAIL_MAILER=mailgun
MAILGUN_DOMAIN=mg.example.com
MAILGUN_SECRET=your-api-key

Ensure MAILGUN_DOMAIN matches your verified domain in Mailgun.

EU vs US Regions

Mailgun has different API endpoints for EU and US regions. Your DNS records are the same, but ensure:

• EU accounts: Use api.eu.mailgun.net
• US accounts: Use api.mailgun.net

The region doesn't affect DKIM setup—just API calls.

Complete Your Email Authentication

Mailgun's verification process includes SPF recommendations, but verify everything:

SPF: Ensure your SPF record includes Mailgun:

include:mailgun.org

Check at spfrecordcheck.com.

DMARC: Set up a DMARC policy. Check at dmarcrecordchecker.com.

Monitor Your DKIM Records

Checking once is good. Monitoring continuously is better. The Email Deliverability Suite watches your SPF, DKIM, DMARC, and MX records daily and alerts you when something breaks.