How do SPF, DKIM, and DMARC email authentication standards work?
Summary
What email marketers say11Marketer opinions
Email marketer from Mailjet explains that DKIM uses a digital signature, which is added to the email header. This signature is validated by the recipient's email server using a public key located in your domain's DNS records. If the signature matches, the email is authenticated, proving it hasn't been tampered with.
Email marketer from EasyDMARC explains that implementing SPF, DKIM, and DMARC together provides a strong defense against email spoofing and phishing attacks. SPF verifies sending sources, DKIM validates message integrity, and DMARC sets the policy and reporting to enforce authentication.
Marketer from Email Geeks recommends Global Cyber Alliance's DMARC Bootcamp for courses on Email Authentication protocols and offers to answer specific questions about DMARC reports via DM.
Marketer from Email Geeks explains that Microsoft often disregards DMARC policies and suggests using the Exchange Admin portal to create inbound rules to enforce DMARC reject policies.
Marketer from Email Geeks shares that Word to the Wise breaks down complicated email concepts in an easy to understand way, providing links to DKIM and SPF articles on the website.
Email marketer from Proofpoint shares that DMARC builds on SPF and DKIM by enabling domain owners to define a policy for how receiving mail servers should handle emails that fail authentication checks. You can choose to have these emails rejected, quarantined, or simply monitored through reports.
Email marketer from URIports explains that DMARC is a tool that allows domain owners to protect their brand from email spoofing. By using DMARC you can gain insight into who is sending emails on your behalf and prevent malicious actors from using your domain to send fraudulent emails.
Marketer from Email Geeks provides a simplified explanation of SPF as a list of approved postmen, DKIM as a digital signature for verifying email integrity, and DMARC as a way to instruct receiving mail servers on how to handle emails that fail authentication, noting Microsoft Exchange's exception to DMARC reject policies.
Email marketer from SparkPost explains that SPF allows you to specify which mail servers are authorized to send email on behalf of your domain. This helps prevent spammers from using your domain to send unauthorized emails. The SPF record is a TXT record in your DNS settings.
Email marketer from TitanHQ explains that understanding email authentication is key to preventing phishing and spoofing attacks. Setting up SPF, DKIM and DMARC correctly prevents impersonation and builds trust with email recipients, improving deliverability.
Email marketer from Postmark shares that proper implementation of email authentication (SPF, DKIM, and DMARC) helps improve email deliverability by ensuring that legitimate emails reach the intended recipients' inboxes. This can increase brand reputation and reduce the risk of email ending up in spam folders.
What the experts say4Expert opinions
Expert from Word to the Wise responds stating that DKIM is a system to verify who sent an email. It is the electronic equivalent of a signature. DKIM adds a digital signature to every email that is sent from your system.
Expert from Email Geeks offers to answer questions about email authentication.
Expert from Word to the Wise explains that DMARC lets the sender tell the receiver what to do with mail that fails authentication (SPF/DKIM). The sender can ask the receiver to reject the email, quarantine it, or do nothing, while also requesting reports about authentication results.
Expert from Word to the Wise explains that SPF, DKIM, and DMARC are mechanisms to vouch for who is sending email using your domain, noting that all three are needed. SPF allows you to declare which IP addresses send mail for your domain. DKIM provides a cryptographic signature. DMARC tells mailbox providers what to do if SPF and DKIM fail and asks for reports about your mail.
What the documentation says4Technical articles
Documentation from Google explains that SPF (Sender Policy Framework) is an email authentication method designed to detect forging sender addresses during the delivery of the email. SPF allows receiving mail servers to verify that mail appearing to come from a specific domain is sent from an IP address authorized by that domain's administrators.
Documentation from Microsoft explains that DKIM (DomainKeys Identified Mail) adds a digital signature to outgoing email messages. Receiving mail servers verify this signature against a public key published in the DNS records. This process confirms that the message wasn't altered during transit and is genuinely from the claimed sender domain.
Documentation from AuthSMTP explains that SPF works by creating a list of authorized IP addresses and domain names that are permitted to send email on behalf of your domain. The recipient mail server checks the SPF record to verify that the sending server is authorized.
Documentation from DMARC.org explains that DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol. It builds upon SPF and DKIM to add a reporting function that allows senders and receivers to improve and monitor protection of the domain from fraudulent email. DMARC helps email providers identify legitimate senders and block malicious actors.