Email Security - Part 3: DKIM

When you send an email, how does the recipient know it’s really from you—and not someone pretending to be you? That’s where DKIM (DomainKeys Identified Mail) comes in.

DKIM is an email security protocol that adds a digital signature to every message you send. This helps verify that the email is authentic and hasn’t been tampered with along the way. It’s one of the key tools—alongside SPF and DMARC—that helps protect your domain from spoofing, phishing, and fraud.

In a Nutshell

DKIM is a security tool installed into your domain that adds a digital signature to your outgoing emails, proving they came from you and haven’t been tampered with. It helps email providers trust your messages, reduces the risk of spoofing, and improves the chances your emails land in inboxes instead of spam.

How DKIM Works

DKIM works by using cryptographic keys—one private and one public.

• Your mail server adds a DKIM signature to each outgoing email using a private key.
• When the recipient gets the email, their mail server checks the public key published in your DNS records to verify the signature.

If the signature matches, it means:

• The email really came from your domain.
• The contents haven’t been altered in transit.

Think of it like sealing a letter in a tamper-proof envelope that only the right recipient can validate.

What a DKIM Record Looks Like

Your DKIM record is a DNS TXT record, usually at a subdomain like:

selector._domainkey.yourdomain.com


The record contains a long public key and looks something like this:

‍v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA...IDAQAB


• v=DKIM1 – Identifies the version.
• k=rsa – Specifies the encryption method.
• p= – Is the public key itself.

This key is used by receiving servers to check whether the DKIM signature on your emails is valid.

Why DKIM Matters

DKIM plays a major role in email security and trust. Here's what it helps with:

• Authenticity – Confirms that the message really came from you.
• Integrity – Verifies that the content hasn’t been changed.
• Reputation – Improves email deliverability and reduces the chance of ending up in spam.
• Protection – Helps block phishing and spoofing attacks using your domain.

Many major providers—like Gmail, Outlook, and Yahoo—use DKIM as a factor in deciding whether to trust your emails.

How to Set Up DKIM

1. Generate a DKIM key pair – Your email provider or server software will give you a public/private key set.
2. Publish the public key – Add it as a TXT record in your DNS under a specific selector.
3. Enable DKIM signing – Your mail server or email platform signs outgoing messages using the private key.
4. Test the setup – Use tools like MXToolbox or Google's CheckMX to verify that DKIM is working properly.

Best Practices for DKIM

• Use at least 2048-bit keys for better security.
• Use a unique selector if you're managing multiple services (e.g. google, mailchimp).
• Rotate keys occasionally to reduce risk in case of compromise.
• Always combine DKIM with SPF and DMARC for complete protection.

Final Thoughts

DKIM helps ensure your emails are trusted, secure, and untampered. It’s invisible to your users but powerful in building trust with email providers and protecting your brand from spoofing.

If you're unsure whether your domain is protected or need help setting up DKIM, SPF, and DMARC, Gaslamp Village Media can guide you every step of the way. Get in touch, and we’ll help lock down your domain and improve your email deliverability.

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