Email Security Protocols: What Do SPF, DKIM and DMARC Do?

Email remains the most fundamental communication tool in business. However, this widespread use also makes email one of the biggest cybersecurity risks . Every day, millions of people unknowingly open emails with malicious links, trust messages from fake senders and put corporate data at risk.

In particular, phishing attacks and spoofed emailscan lead to serious data breaches for both individuals and organizations. Worse still, attacks that use a company's domain name can damage the brand's credibility and cause serious reputational harm.

This is where three important protocols that make email traffic more secure come in:

• SPF (Sender Policy Framework)
• DKIM (DomainKeys Identified Mail)
• DMARC (Domain-based Message Authentication, Reporting and Conformance)

These three are the cornerstones of protecting your domain and email infrastructure. In this series, we explain in detail what each protocol does, how it works and why they should be used together.

What Is SPF (Sender Policy Framework), and What Does It Do?

Email is one of the most widely used communication methods, especially in the corporate world. However, it is also one of the most common tools of cyberattacks. Phishing attacks that use fake sender addresses mislead users and try to steal personal information. The SPF protocol is one of the core security measures developed against this threat.

What Is SPF?

SPF (Sender Policy Framework) is an email authentication protocol that defines which IP addresses are authorized to send email for a domain. With SPF, receiving servers can verify whether the server that sent an email really belongs to the domain in question.

This control mechanism helps prevent malicious actors from using your domain without authorization.

How Does SPF Work?

SPF works through DNS (the Domain Name System). A special SPF record added to the sending domain's DNS records lists the IP addresses authorized to send email from that domain.

When an email is sent, the process works as follows:

1. The receiving server queries the SPF record of the domain in the sender address of the incoming email.
2. The IP addresses in the SPF record are compared with the IP address of the server that sent the email.
3. If the IP address is listed in the SPF record, the check passes.
4. If there is no match, the receiving server can reject the email, quarantine it or issue a warning, depending on the SPF policy.

Why Is SPF Important?

• It helps prevent attacks that use fake sender addresses.
• It stops malicious actors from impersonating your domain.
• It increases the trustworthiness of your corporate email traffic.
• It has a positive effect with spam filters.

How Do You Create an SPF Record?

An SPF record is defined as a TXT record in DNS. A sample SPF record might look like this:

v=spf1 ip4:192.168.1.1 include:yourmailservice.com -all

This record states that email must not be sent from any source other than a specific IP address and an authorized external service (for example a newsletter tool).

Note: SPF alone does not provide sufficient protection. It only checks whether the sending server is authorized; it does not verify the content of the email or whether it has been altered. For this reason, you should always use SPF together with the DKIM and DMARC protocols.

What Is DKIM (DomainKeys Identified Mail), and What Does It Do?

The SPF protocol checks whether an email was sent from an authorized server. However, this does not mean that the content of the email was not altered in transit. This is where DKIM comes in.

DKIM is an authentication protocol that detects whether an email really belongs to the domain it was sent from and whether it was tampered with in transit.

What Is DKIM?

DKIM (DomainKeys Identified Mail) is a security protocol that digitally signs outgoing emails. The receiving server verifies this signature and determines:

• Whether the email was sent by an authorized sender,
• Whether its content was altered in transit.

This protects not only technical authentication but also message integrity.

How Does DKIM Work?

DKIM is a system based on cryptographic methods. The process works as follows:

1. When the email is created, the sending server adds a digital signature to specific parts of the message.
2. This signature is generated with a private key that belongs to the domain.
3. The receiving server verifies the signature with the public DKIM key published in the sender's DNS records.
4. If the signature is valid, the email is verified. If not, the message is assumed to be altered or fake.

Why Is DKIM Important?

• It verifies whether the content was altered during email transmission.
• It helps prevent misuse of the domain.
• It provides a second layer of verification against phishing and spoofed email attacks
• It increases the trustworthiness of email sending and has a positive effect on delivery rates.

How Do You Add a DKIM Record?

During DKIM setup:

• A private key
  for your domain is configured on the server.
• The corresponding public key
  is published as a TXT record in DNS.

A sample DKIM DNS record format might look like this:

default._domainkey.yourcompany.com IN TXT "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFA…"

Receiving servers need this record to perform verification.

DKIM alone does not provide complete security either. It offers stronger protection when used together with SPF. However, for an integrated, controlled setup, these two protocols must work together with DMARC .

What Is DMARC (Domain-based Message Authentication, Reporting and Conformance), and What Does It Do?

Protocols such as SPF and DKIM largely prevent unauthorized use of domains and improve email security. However, these two protocols are not enough on their own, because there is no standard definition of how the receiving system should respond when SPF or DKIM verification fails.

This is exactly where DMARC comes in.

What Is DMARC?

DMARC (Domain-based Message Authentication, Reporting and Conformance) is a policy that tells receiving servers how to handle an email based on SPF and DKIM verification results. DMARC also gives domain owners reporting capabilities so they can monitor anomalies in their email traffic.

DMARC lets domain owners manage their defenses against impersonation.

How Does DMARC Work?

DMARC checks whether the SPF and/or DKIM protocols are applied and whether they pass. Based on this check, it acts according to the defined policy. The process works as follows:

1. The receiving server performs SPF and DKIM verification for the incoming email.
2. If one or both of these checks fail, the receiving server queries the DMARC policy.
3. Depending on the rules defined in the DMARC record, one of the following actions is applied to the email:

• none
  : Report only; take no action.
• quarantine
  : Quarantine the email (for example, send it to the spam folder).
• reject
  : Reject the email completely.

1. Receiving servers also send DMARC reports to the domain owner at regular intervals.

Why Is DMARC Important?

• It enforces effective application of SPF and DKIM checks.
• It allows organizations to identify fake emails that impersonate their domains.
• It makes it possible to take direct action against phishing attacks.
• Its reporting feature helps you analyze where potential threats come from and how.
• It protects brand reputation and customer trust.

How Do You Create a DMARC Record?

A DMARC record is a TXT record added to DNS. A sample DMARC record might look like this:

_dmarc.yourcompany.com IN TXT "v=DMARC1; p=reject; rua=mailto:dmarc-reports@yourcompany.com"

This record specifies:

• That the DMARC protocol is active (
  v=DMARC1
  )
• That, as policy, emails that fail checks will be rejected (
  p=reject
  )
• Which email address reports will be sent to (
  rua=…
  )

.

DMARC works together with SPF and DKIM to create a three-layer protection. However, this setup is effective only when it is configured correctly. Incorrect configurations can also block legitimate emails. For this reason, we recommend testing before rollout and a phased transition.

When these three systems are used together:

• Your domain gets strong protection against unauthorized use.
• Phishing and spoofed email attacks are largely blocked.
• Email sending reliability increases and delivery rates improve.
• Brand reputation and customer trust are protected.

Equipping your corporate email infrastructure with these three protocols is not just a technical choice; it is the foundation of your digital security.

The Right Partner for a Secure Email Infrastructure: Synchron Bilişim

Security protocols such as SPF, DKIM and DMARC are essential elements of a modern email infrastructure. However, setting up, managing and sustaining these systems correctly requires technical knowledge, experience and continuity.

At Synchron Bilişim , we provide scalable, secure and manageable corporate email services tailored to your business.
Our services include:

• Professional email setup for your domain
• Full integration of security protocols such as SPF, DKIM and DMARC
• Advanced spam filtering and virus protection
• Backup, archiving and data recovery solutions
• 24/7 technical support and uninterrupted service

We are here to make your email communication not just functional but also secure and enterprise-grade . For more information, contact us.