Do you know what DKIM and DMARC is and how they affect the deliverability of your emails?

In the field of email marketing there are many abbreviations that might not be commonly seen within the basic users’ community, yet, due to their connection to the email deliverability, they are vital for the marketing managers. Their familiarity and correct usage can even help reduce loss of reputation and furthermore lead to the domain and label protection from spammers and phishing. Let’s make a brief introduction.


The biggest flaw of electronic mail is that in order to send an email every user can use a random address, even though it may not belong to him or her. There are various systems that can help the mailing recipient identify whether the sender is authorized to use the specific email address or not. One of these systems is DKIM (Domain Keys Identified Mail) which has been used by providers for many years. Although the technology is similar to SPF (Sender Policy Framework) DKIM offers one crucial benefit. While SPF connects the domain sender to a specific IP address from which the mail can be sent, DKIM uses the electronic signature that is generated on the sender’s server and has no connections to any specific IP address. DKIM only manifests by adding DKIM Signature heading that includes the electronic signature generated by SMTP server sender. Thus, unlike in the case of classical electronic signatures, there are no demands on the end-user. That is even, for example, when it comes to certificate expiration or support of the root certificate in the email client.


DMARC (Domain-based Message Authentication, Reporting & Conformance) is a specification that provides a connection of both of the above mentioned technologies, authentication SPF and DKIM. It informs the mail receiving server of the rules it should apply on mails incoming from specific domains. Though DMARC goes further as its goal is not only the identification of the rules-exchange communication but their partial replacement and broadening. While SPF communicates the rules on how to deal with mail whose origin is not in accordance with the defined IP address, DKIM does not define whether the signature must exist, it only allows for already existing signature’s validation. DMARC thus requires the existence of both SPF and DKIM and establishes the management process of the mail that is not in accordance with DMARC domain rules. It also allows for the rules to be applied to just a fragment of the mail and establishes the further proceeding of the mail that deviates (quarantine or refusal). However, it simultaneously defines feedback methods that allow the domain owner to receive reports on the DMARC rules application and on the amount of mail that was in accordance with the rules and the mail that deviated. This includes information on the origin and mechanisms of the deviants.

What does that mean?

Many companies using email marketing are facing various changes in relation to DKIM/DMARC. Great global freemail providers (e.g. Gmail, Hotmail, Yahoo…) have had a long-established set of rules for filtering mail from unauthorized senders using their domain. Except for being protected from personality fraud, these functions do not have much impact on the domain’s basic users. However, it does have a great impact on companies that are using popular freemail services’ email addresses for their communication, which is fundamentally wrong. It can be expected that sooner or later DKIM/DMARC will be gradually introduced to all email service providers as it is the only way to protect their addresses and radically reduce SPAM. For professional marketers, this means an emphasis on the use of high-quality solutions in email marketing that is supported by both DKIM and DMARC. Small marketing mail senders can see this as an impulse for obtaining their own domains and terminating freemail services communications for which they may have been already penalized by SPAM filters.

Better Deliverability with us also offers native support of the authentication methods DKIM and DMARC for all our clients. If you are our client, we strongly recommend a proper setting of DNS entries at the domain through which you communicate, in order to achieve an optimal level of deliverability. This setting will highly improve the deliverability of the emails distributed via A step-by-step guide on how to proceed can be found in our article here. Below you can see the difference between the heading of an email with enabled DKIM and without.

Check your DNS records

You may check your DNS setting right here.

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