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MX, SPF, DKIM, and DMARC in plain words: why a company’s mail reaches the inbox

Explaining the basic DNS records for corporate email: what MX does, why SPF and DKIM are needed, and how DMARC reduces the risk of domain spoofing.

DNS and security 3 min
Infographic of the MX SPF DKIM DMARC DNS records

A company’s email can look correctly set up on the surface, yet messages still go to spam. A common reason is incomplete or conflicting DNS records.

MX, SPF, DKIM, and DMARC are not “technical magic” but four layers of trust in a domain. They help mail systems understand where to accept mail and whom to trust when sending.

DNS chain

How a domain proves a message is genuine

  1. 01MX accepts
  2. 02SPF allows
  3. 03DKIM signs
  4. 04DMARC sets the rule
  • SPF must account for every sending service
  • DKIM verifies the message signature
  • DMARC helps fight domain spoofing

MX: where to deliver mail

The MX record tells the world which servers accept mail for the domain. If MX points to the wrong place or conflicts with an old service, inbound messages can be lost or arrive in the old system.

Before switching MX, it is important to understand where the mail is now and whether there is backup access to the old mailbox.

SPF: who is allowed to send

SPF lists the services allowed to send mail on behalf of the domain. This can be a mail platform, an accounting system, a website, a mailing service, or accounting software.

The error appears when a new service is connected but forgotten in SPF. From the outside the message looks suspicious, even if a real employee sent it.

DKIM: the signature of outgoing mail

DKIM adds a digital signature that lets the receiving side know the message was not altered in transit and is genuinely tied to your domain.

For business this matters especially for invoices, proposals, and support mail, where trust in the sender affects how fast the client replies.

DMARC: the trust policy

DMARC ties SPF and DKIM into a clear rule: what to do with messages that fail the check. It is better to start gently, in monitoring mode, and then tighten the policy.

That way you can see the real sources of sending and avoid accidentally blocking your own services.

Quick checklist

  • Check the current MX
  • Gather all sending services
  • Update SPF
  • Enable DKIM
  • Start DMARC in monitoring mode

What to do next

KMVSG checks the domain’s DNS records, finds conflicts, and helps configure corporate email deliverability.

Discuss your task

This article covers: MX SPF DKIM DMARC, DNS setup for email, mail going to spam, corporate email security.