Why your emails go to spam — and how to fix it

You hit send, the email looks fine to you — and it lands in the recipient's spam folder, or vanishes entirely. It's one of the most frustrating problems in running a small business, because nothing on your screen tells you it happened. The cause is almost always the same: your domain's DNS doesn't properly vouch for your mail, so receiving servers treat it with suspicion. Three records fix it.

1. SPF — say who's allowed to send as you

SPF (Sender Policy Framework) is a single line in your DNS that lists which servers are permitted to send email using your domain. When a server receives a message claiming to be from you, it checks whether it actually came from one of those approved sources. No SPF record, or a messy one, and your mail looks like it could be forged — straight to spam. You should have exactly one SPF record, and it should end in ~all (softfail) or -all (hardfail). Two SPF records is invalid and can cause everything to fail, so if you add a new sending service, you merge it into the existing record rather than creating a second one.

2. DKIM — sign your mail so it can't be faked

DKIM (DomainKeys Identified Mail) adds an invisible cryptographic signature to every message you send. The receiving server checks that signature against a public key published in your DNS. If it matches, the server knows the message genuinely came from you and wasn't tampered with on the way. Setting it up usually means switching on DKIM in your mail provider and pasting the key it gives you into your DNS. It's the single biggest trust signal you can add.

3. DMARC — tell servers what to do with fakes

DMARC ties SPF and DKIM together and gives receiving servers an instruction for mail that fails both: do nothing (p=none — monitor only), send it to spam (p=quarantine), or reject it outright (p=reject). It's your defence against scammers spoofing your domain to phish your customers. Start at p=none to watch what's happening, then tighten to quarantine once you're confident your legitimate mail passes.

The quick wins beyond DNS

• Send from a real address on your own domain (you@yourbusiness.co.uk), never a no-reply or a free webmail address pretending to be your brand.
• Avoid spammy subject lines, ALL CAPS, and a wall of links or images with no text.
• Warm up a new domain gradually — don't blast a thousand emails on day one.
• Always include a working unsubscribe link in bulk mail; it's the law in the UK and EU, and it protects your reputation.

Check yours in ten seconds

Not sure where you stand? Our free email deliverability checker inspects your domain's MX, SPF, DKIM and DMARC records live and tells you, in plain English, what's set up and what's missing. If it flags gaps, the lasting fix is mail hosting that configures all of this for you — which is exactly what comes with a Centaur mailbox on your own domain, so your invoices and replies land in the inbox rather than the spam folder.