How to Avoid Spam: Complete 2026 Guide

Every day, roughly 45% of emails sent worldwide get classified as spam. If your business emails regularly land in your customers' junk folders, you are losing revenue without even knowing it. Quotes never read, order confirmations ignored, newsletters nobody opens: the problem is not the content, it is the technical configuration of your domain.

In this guide we explain — simply and practically — the three pillars of email deliverability: SPF, DKIM and DMARC. By the end you will know exactly what to check and how to verify that everything works.

Why do emails end up in spam?

Providers like Gmail, Outlook and Yahoo use increasingly sophisticated filters to protect users. These filters do not just look at message content — they look above all at the technical identity of the sender. If your domain cannot prove it is legitimate, the message gets downgraded or blocked entirely.

Since February 2024, Google and Yahoo have made email authentication mandatory for anyone sending more than 5,000 messages per day. But even at smaller volumes, a correct configuration makes the difference between reaching the inbox and vanishing into the void.

SPF: who is authorised to send on your behalf

SPF (Sender Policy Framework) is a DNS record listing the servers authorised to send email from your domain. When a receiving server gets an email from yourdomain.com, it checks the SPF record to verify that the sending server is on the list.

Without SPF, anyone could send email pretending to be you. With SPF misconfigured, even your own tools (CRM, newsletter platform, Google Workspace) may end up flagged as unauthorised.

Common SPF mistakes

• Forgetting to include every service that sends email (Mailchimp, HubSpot, etc.)
• Having more than one SPF record on the same domain (only one is allowed)
• Exceeding the 10 DNS lookup limit, which invalidates the whole record
• Using +all instead of ~all or -all

DKIM: the digital signature of your emails

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to each outgoing email. The receiving server uses the public key (published in your domain's DNS) to verify that the message has not been altered during transit.

Think of DKIM as a digital wax seal: it guarantees that the email is authentic and intact. Without DKIM, providers cannot distinguish your legitimate emails from forgeries.

DMARC: the policy that ties it all together

DMARC (Domain-based Message Authentication, Reporting and Conformance) is the third pillar. It works like a supervisor: it tells receiving servers what to do when an email fails SPF and DKIM checks.

With DMARC you can choose between three policies:

• p=none — monitor without blocking (useful to start)
• p=quarantine — send suspicious emails to spam
• p=reject — reject unauthenticated emails outright

The advice is to start with p=none to gather data, analyse reports, and progressively tighten up to p=reject.

How to verify your configuration

The fastest way to test everything is mail-tester.com. Just send an email to the temporary address it provides and within seconds you get a score from 1 to 10 with a detailed analysis of SPF, DKIM, DMARC and other factors.

A score below 7 on mail-tester.com means a significant percentage of your emails is not reaching its destination. The realistic target is 9 or 10.

Other useful tools include MXToolbox for DNS record analysis, Google Postmaster Tools to monitor your domain reputation on Gmail, and the aggregated DMARC reports you automatically receive once DMARC is configured.

The mistakes we see most often

Working with dozens of companies, these are the recurring problems:

• Corporate email configured only through the hosting provider, with no dedicated SPF/DKIM
• Migration to Google Workspace or Microsoft 365 without updating DNS records
• Newsletters sent from an external service not included in the SPF record
• DMARC absent or stuck on p=none for years without ever moving to the next step
• Missing or incorrect PTR (reverse DNS) record on the mail server

Quick checklist for 2026

• Make sure you have a single SPF record that includes every sending service
• Enable DKIM for every service that sends email from your domain
• Configure DMARC at least in monitoring mode
• Test with mail-tester.com and aim for 10/10
• Review DMARC reports weekly during the first month
• Do not use free email addresses (Gmail, Yahoo) for business communications