Skip to content
Modern Work AI Business Solutions

Understanding DMARC: Protecting Your Domain and Your Reputation

Why DMARC is becoming a basic requirement for protecting domains, customers and trust.

Know who sends for you

Understand every domain and every legitimate service sending email on your organisation's behalf. 

Authenticate First

SPF and DKIM provide the evidence DMARC uses to assess whether messages are properly authenticated and aligned. 

Move towards enforcement

Use reporting and evidence to progress safely from monitoring towards quarantine and reject. 

Email security and domain authentication solve different parts of the problem

Most businesses already apply controls to protect the email arriving in their environment. Domain authentication addresses a different question: how can receiving businesses establish whether a message claiming to come from your domain is properly authenticated? 

SPF
priority

Identifies the systems authorised to send email for a domain.

DKIM
priority

Uses a cryptographic signature to help verify that a message is authentic and has not been altered.

DMARC
priority

Checks alignment, provides reporting and tells receiving systems what to do when authentication fails.

A DMARC Record is a Starting Point, not the Whole Story

The policy attached to the DMARC record determines how participating receiving systems are asked to handle messages that fail the required checks. Explore the three common policy states below.

p=none - Monitor
The domain receives monitoring information, but the policy does not ask receiving systems to quarantine or reject failing messages. This is where organisations typically start when deploying DMARC.

p=quarantine - Begin enforcement
Messages that fail DMARC can be treated as suspicious and may be directed to spam or quarantine. Enforcement has begun, but the messages are not necessarily rejected.

p=reject - Enforce
Receiving systems are instructed to reject messages that fail DMARC. When correctly implemented, this is the strongest protection against exact-domain impersonation.

Event image 3 with blur 800x800

Why Businesses Progress Towards Enforcement

Legitimate email often comes from more than Microsoft 365. CRM platforms, finance applications, service desks, HR platforms, websites and other cloud services may all send on an organisation's behalf. Moving safely to enforcement means understanding those senders first.

1. Discover

Identify owned domains and legitimate sending services.

2. Authenticate

Configure and validate SPF and DKIM for authorised sources.

3. Monitor

Use DMARC reporting to understand genuine and unauthorised traffic.

4. Enforce

Progress deliberately towards quarantine and reject using evidence.

5. Maintain

Review the position as domains, suppliers and sending services change.

Businesses are at different stages of the DMARC journey

30 of 50
had not reached full DMARC enforcement
21 of 50
had no DMARC record or were operating at p=none.
26 of 50
had an identified SPF issue

A review of the publicly available email-authentication posture of 50 UK-based businesses across various industries found a mixture of DMARC maturity levels. The organisations and domains are intentionally not identified. 

The purpose of these figures is to illustrate that DMARC adoption is a maturity journey, not to characterise any individual organisation's security posture. 

DMARC Supports Security, Trust and Reliable Email

Customers and partners
priority

DMARC helps reduce the opportunity for exact-domain impersonation to be used against people who trust your organisation.

Reliable delivery
priority

Correct authentication gives receiving platforms clearer evidence that legitimate messages come from an authorised source.

Sender expectations
priority

Major mailbox providers have introduced authentication requirements for bulk senders, making email authentication part of maintaining trustworthy, supportable delivery.

DMARC in Practice

UD26 Images 800x600-05
Node4 Derby-85
User Day Greeting Desk
Node4 Derby-67 (1)

Build confidence in your domain-authentication position

Start with evidence. A review of public email-authentication configuration can establish the current DMARC policy and highlight obvious SPF or configuration issues. It cannot, on its own, prove that every legitimate sender is known or correctly aligned. 

  • check
    check

    Review your domains

    Identify the domains that need to be understood and governed.

  • check
    check

    Identify legitimate senders

    Map Microsoft 365 and other services sending email on your behalf.

  • check
    check

    Validate authentication

    Check SPF and DKIM for authorised sending sources.

  • check
    check

    Understand DMARC policy

    Confirm whether each domain is monitoring, quarantining or rejecting failures.

  • check
    check

    Resolve legitimate failures

    Correct authentication before strengthening enforcement.

  • check
    check

    Progress deliberately

    Move towards the appropriate enforcement state using evidence rather than guesswork.

  • check
    check

    Document ownership

    Make responsibility for domain authentication clear.

  • check
    check

    Review periodically

    Reassess as applications, suppliers and domains change.

Want greater confidence in your email-authentication position?

Node4 can assess your publicly visible email-authentication posture, help identify gaps across DMARC, SPF and DKIM, and define the work required to progress safely towards enforcement.