Guides, tools and research
Everything you need to understand and improve your domain security posture. Free guides, 20 instant tools, and original research.
UK Public Sector DMARC Tracker
Every .gov.uk domain, rescanned daily since NCSC Mail Check retired. DMARC policy, enforcement, and where aggregate reports actually go.
Updated quarterly with fresh data. Downloadable tables and regional breakdowns included.
Showing 64 of 64 resources
NCSC and Cyber Essentials Email Security Requirements for UK Public Sector Suppliers
Cyber Essentials does not require DMARC, SPF or DKIM. What the certificate actually covers, which NCSC guidance the email questions really come from, and what changed when Mail Check retired.
What is SPF? Sender Policy Framework Explained
What SPF means, how it works, which address it checks, ~all vs -all, the 10-lookup limit, and why SPF needs DKIM and DMARC.
Why is My DMARC Failing? Causes and Fixes
The real reasons DMARC fails: alignment, broken DKIM, forwarding, unauthorised senders and strict alignment, each with a symptom, diagnosis and fix.
Bulk Sender Requirements 2026: Google, Yahoo and Microsoft
What Google, Yahoo and Microsoft require from bulk senders in 2026: SPF, DKIM, DMARC alignment, one-click unsubscribe and spam-rate limits, mapped to the DNS controls that satisfy them.
DMARC for MSPs: Managing Email Security Across Client Domains
An operational playbook for UK MSPs running DMARC across many client tenants: auditing, bulk onboarding, per-client white-label reporting, alignment and pricing that scales.
How to Move from DMARC p=none to p=reject (Step by Step)
A report-driven path from p=none to p=reject: read the aggregate reports, authorise every legitimate sender, then advance to quarantine and reject once the data is clean.
Free DMARC Tools Compared: Checkers, Generators and Report Viewers
An honest map of the free DMARC tool landscape in 2026, what each one really gives you, the limits of free tiers, and when a multi-domain team should move to a paid platform.
DNS and AI Discovery: How AI Crawlers and Agents Find and Trust Your Domain
The honest 2026 picture of AI discovery: robots.txt AI controls, Cloudflare Content Signals, llms.txt and .well-known agent cards on the HTTP layer, and the DNS identity layer (SPF, DKIM, DMARC, MTA-STS, DNSSEC) that makes your domain trustworthy.
UK MSP DMARC Audit: Q2 2026
192 UK MSPs graded A+ to F on the Security Grade. The average UK MSP scores a C; only 6% earn an A. Transport security is the ceiling.
DMARC for Parked and Non-Sending Domains
How to set up DMARC for a parked domain that never sends email. NULL MX, SPF -all, p=reject and DKIM revocation, with RFC, NCSC and M3AAWG sources.
Best DMARC Monitoring Tools UK 2026
UK-focused 2026 comparison of ShieldMarc, dmarcian, EasyDMARC, PowerDMARC, Valimail, Red Sift and Sendmarc. Pricing, features, data residency and best fit for UK MSPs, multi-domain IT teams, NHS trusts and enterprise.
What We're Building and When You Can Use It
A progress update on the ShieldMarc platform: what we are working on, when we expect to open to the public, and how to start a free trial.
How to Set Up DMARC for Google Workspace
Step-by-step guide to configuring DMARC, SPF, and DKIM for Google Workspace. Protect your domain from spoofing and improve Gmail deliverability.
How to Set Up DMARC for Office 365 and Microsoft 365
Set up SPF, DKIM and DMARC for Office 365 and Microsoft 365: current Defender portal steps, the onmicrosoft.com record, and how to check it worked.
What is BIMI? Brand Indicators for Message Identification Explained
How BIMI displays your verified logo in Gmail, Apple Mail, and Yahoo, and what a VMC actually costs.
DMARC p=quarantine vs p=reject: Which Policy Should You Use?
When to pick quarantine, when to pick reject, and how to move between them without breaking mail flow.
DMARC for the NHS and UK Public Sector: A Post Mail Check Guide
How NHS trusts, councils, and gov.uk bodies can replace NCSC Mail Check with a UK owned, EU hosted platform.
Our Mission: AI Tools, Open to All
Why we built ShieldMarc with free AI-powered tools at its core, and what we believe about access, protection, and the future of email security.
How ShieldMarc Threat Detection Works
Every DMARC report row is evaluated by a multi-signal scoring engine and AI evaluation to separate genuine threats from noise. Here is how it works.
Why Modern DMARC Monitoring Costs a Fraction of Legacy Tools
Legacy DMARC platforms carry years of technical debt. We built ShieldMarc from scratch in 2026 with modern tooling and zero bloat.
UK MSP DMARC Audit: Q1 2026
192 UK MSPs analysed across DMARC, SPF, SSL, DNSSEC, and brand domain protection.
What is DMARC? A Plain English Guide
DMARC explained for IT teams. What it does, how it works, and why you need it.
SPF vs DKIM vs DMARC: What's the Difference?
How SPF, DKIM, and DMARC work together to protect your domain from spoofing.
How to Read DMARC Reports: RUA and RUF
How to read and act on DMARC aggregate and forensic reports.
SPF Hard Fail vs Soft Fail: Why ~all Is Safer with DMARC
When to use -all vs ~all in your SPF record and how DMARC changes the equation.
How to Fix SPF Too Many DNS Lookups
Diagnose and fix the 10 DNS lookup limit in SPF records.
NCSC Mail Check Has Retired: What UK Organisations Should Do Now
What the NCSC Mail Check retirement means and how to replace it.
SSL Certificate Monitoring: What to Check and When
Avoid certificate expiry incidents with proactive SSL monitoring.
What is MTA-STS and TLS-RPT? Securing Email in Transit
How MTA-STS enforces TLS for inbound email and TLS-RPT captures delivery failures.
What is DNSSEC? How DNS Signing Protects Your Domain
How DNSSEC prevents DNS spoofing and cache poisoning attacks.
CAA Records Explained: Control Who Issues Your SSL Certificates
Use CAA records to restrict which certificate authorities can issue certs for your domain.
DNS Record Types Explained: A, AAAA, MX, TXT, CNAME and More
A guide to every common DNS record type and what it does.
Domain Expiry and WHOIS: How to Protect Your Registration
Prevent domain hijacking and accidental lapses with registration monitoring.
Protecting Your Brand from Lookalike Domains
Detect and defend against typosquatting and brand impersonation domains.
How to Create SPF, DKIM, and DMARC Records: Step-by-Step
A step-by-step walkthrough for setting up email authentication from scratch.
How to Set Up DKIM: Step-by-Step for Every Email Provider
Provider-specific DKIM setup guides for Google Workspace, Microsoft 365, SendGrid, Mailchimp, and more.
ShieldMarc vs EasyDMARC
A straight comparison for UK MSPs: pricing, message volume, AI model, posture and support.
ShieldMarc vs dmarcian
A straight comparison for UK MSPs: pricing, message volume, AI model, posture and support.
ShieldMarc vs Valimail
A practical alternative to enterprise-priced DMARC. Published pricing, self-serve onboarding, 30-day trial.
ShieldMarc vs PowerDMARC
Flat pricing vs volume-tiered plans: domains per pound, in-tier price step-ups, hosting and certifications compared honestly.
ShieldMarc vs Red Sift OnDMARC
Two UK platforms compared: flat multi-domain pricing and monitoring breadth vs Red Sift's certifications and hosted record management.
ShieldMarc vs Sendmarc
Published flat pricing and self-serve onboarding vs Sendmarc's quote-based, partner-first sales model.
ShieldMarc vs DMARCLY
Mid-size economics, full-year retention and whole-domain monitoring vs DMARCLY's budget tier steps.
ShieldMarc vs Mimecast DMARC Analyzer
A standalone DMARC platform with published flat pricing against a product quoted inside an enterprise email-security portfolio.
Security Grade
Run 16 security checks and get an A+ to F grade.
SPF, DKIM & DMARC Checker
Check your DMARC policy, SPF record, and DKIM selectors in one scan.
SPF Checker
Check any domain's SPF record: mechanisms, DNS lookup count, include tree and fail policy.
DKIM Checker
Scan common DKIM selectors and verify public keys for any domain.
SSL Certificate Checker
Inspect certificates, expiry dates, and chain validity.
DNS Lookup
Query any DNS record type instantly.
SPF Flattener
Resolve SPF includes to a flat list of IPs.
Lookalike Domain Scanner
Detect typosquat and impersonation domains.
DNSSEC Checker
Verify DNSSEC signing on any domain.
MTA-STS Checker
Check MTA-STS policy and TLS enforcement.
TLS-RPT Checker
Verify TLS-RPT reporting records.
CAA Checker
Inspect CAA records and certificate issuance restrictions.
Domain Expiry Checker
Check domain registration status and expiry dates.
WHOIS Lookup
Query domain registration and ownership data.
DMARC Record Generator
Build a valid DMARC record in seconds.
SPF Record Generator
Create an SPF record with your email providers.
DKIM Record Generator
Generate a DKIM DNS record for your domain.
CAA Record Generator
Build CAA records to restrict certificate issuance.
DMARC Report Viewer
Upload and parse DMARC aggregate XML reports.
Email Header Analyser
Paste email headers and see authentication results, routing hops, and delays.
Where to start
If DMARC is new to you, begin with the guides. They assume no prior knowledge of email authentication and build up from what SPF and DKIM actually do to why DMARC needs both, then to reading the reports that arrive once a policy is live. The most common failure is not a misconfigured record but moving to an enforcing policy before knowing every legitimate sender, so the guides spend time on discovery rather than syntax.
If you manage domains for other organisations, the research section is likely more useful. It contains original audits of how UK organisations actually configure email authentication, drawn from published DNS records, with the sample and method stated so you can reproduce or challenge the numbers.
Public sector teams working through the retirement of NCSC Mail Check will find the migration material under guides, covering what Mail Check provided, what has to be replaced, and which parts have no direct equivalent. The engineering section is a different audience again: it documents how ShieldMarc itself is built, for readers evaluating whether the detection claims hold up.