Spam is something we all deal with. However, if you own the domain from which spam emails appear to originate, the consequences can be severe. Email spoofing is real, and every domain owner should take steps to ensure their domain is not exploited by spammers and scammers.

For business owners, it is crucial to implement basic security measures to prevent domain and email spoofing. Ensuring proper email authentication protocols are in place can help protect both your brand and your customers from malicious attacks.

A good writeup is available at the following links:

https://www.zoho.com/mail/help/adminconsole/spf-configuration.html

https://www.zoho.com/mail/help/adminconsole/dkim-configuration.html

https://www.zoho.com/mail/help/adminconsole/dmarc-policy.html

DKIM (DomainKeys Identified Mail)

DKIM is an email authentication method designed to detect forged sender addresses in email messages. It allows an organization to sign its outgoing emails with a cryptographic signature, which receiving mail servers can verify using the sender’s public key published in the domain’s DNS records.

How DKIM Works

1. Signing Emails: The sending mail server generates a unique DKIM signature using a private key and embeds it in the email’s header.
2. Publishing the Public Key: The domain owner publishes the corresponding public key as a TXT record in the domain’s DNS.
3. Verifying Emails: The recipient’s mail server retrieves the public key from DNS and validates the email’s DKIM signature. If the signature is valid, the email is considered authentic.

SPF (Sender Policy Framework)

SPF is an email authentication protocol that helps prevent email spoofing by specifying which mail servers are authorized to send emails on behalf of a domain. It works by allowing domain owners to publish a TXT record in their DNS settings, listing the mail servers permitted to send emails using their domain.

How SPF Works

1. DNS Record Setup: The domain owner publishes an SPF TXT record in their DNS settings, specifying allowed mail servers.
2. Email Transmission: When an email is sent, the recipient’s server queries the sender’s domain for the SPF record.
3. Verification: The recipient’s server checks if the sending server’s IP address matches the authorized list in the SPF record.
4. Pass or Fail Decision: If the email comes from an authorized server, it is accepted. Otherwise, it may be rejected or marked as spam.

DMARC (Domain based Message Authentication, Reporting, and Conformance)

DMARC is an email security protocol that builds upon SPF and DKIM to prevent email spoofing. It provides domain owners with visibility into email activity and enforces policies to reject or quarantine unauthorized emails.

How DMARC Works

1. Email Authentication: DMARC relies on SPF and DKIM to authenticate emails. The recipient server checks if the sender’s domain has valid SPF and/or DKIM signatures.
2. Policy Enforcement: Based on the domain’s DMARC policy (none, quarantine, or reject), the receiving server determines how to handle unauthenticated emails:
   • p=none: The email is delivered normally, but reports are generated.
   • p=quarantine: Suspicious emails are sent to the spam folder.
   • p=reject: Unauthenticated emails are rejected outright.
3. Reporting Mechanism: DMARC provides reports (rua for aggregate reports, ruf for forensic reports) to help domain owners monitor email authentication activity and detect unauthorized usage.