Question 1

What is DMARC and why does my business need it?

Accepted Answer

DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication protocol that tells receiving mail servers what to do with emails that fail SPF or DKIM checks — either quarantine or reject them. Without DMARC, attackers can send emails that appear to come from your domain (email spoofing), enabling phishing attacks that impersonate your business. DMARC is now required by Google and Microsoft for bulk senders, and is a key control assessed in Cyber Essentials.

Question 2

What is the difference between SPF, DKIM, and DMARC?

Accepted Answer

SPF (Sender Policy Framework) specifies which mail servers are authorised to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing emails that verifies they haven't been tampered with. DMARC ties both together — it tells receiving servers what to do when SPF or DKIM checks fail, and sends you reports on who is sending email from your domain. All three need to be correctly configured for full email authentication.

Question 3

How long does DMARC setup take?

Accepted Answer

A basic DMARC implementation (SPF, DKIM, DMARC in monitoring mode) typically takes 1–2 business days. Moving from monitoring mode to enforcement (quarantine or reject policy) takes 2–6 weeks, as we analyse DMARC reports to ensure legitimate email sources are not blocked. Coreitech manages the full process from initial audit through to enforcement and ongoing reporting.

Question 4

Will DMARC break my legitimate emails?

Accepted Answer

If configured correctly, DMARC will not break legitimate emails. The risk of disruption comes from misconfiguration — setting too aggressive a policy before all legitimate sending sources are verified. Coreitech starts every DMARC deployment in monitoring mode (p=none), analyses the reports to identify all legitimate senders (including CRMs, marketing platforms, and third-party services), and only moves to enforcement once we are confident nothing will break.

Question 5

Does DMARC protect against phishing?

Accepted Answer

DMARC protects against email spoofing — where attackers send emails that appear to come from your domain. This is a common vector for phishing attacks targeting your customers, suppliers, and employees. However, DMARC alone does not block all phishing — attackers can still register lookalike domains (e.g. c0reitech.co.uk). A complete email security solution combines DMARC with Defender for Office 365 anti-phishing, Safe Links, impersonation protection, and security awareness training.

DMARC &
EMAIL SECURITY
LONDON

DMARC & email security — frequently asked questions

Secure your email domain today

DMARC &EMAIL SECURITYLONDON

DMARC & email security — frequently asked questions

Secure your email domain today

DMARC &
EMAIL SECURITY
LONDON