How to use email tools to fix deliverability (MX, SPF, DKIM, blacklists)

"My email is not arriving" almost always comes down to one of four things: mail is going to the wrong server, your domain is not authorised to send, your sending IP is blacklisted, or the connection itself fails. Each has a free tool that pins it down in a minute. Start at the free tools hub.

1. Is mail routed correctly? — MX record checker

Use the MX record checker. It shows the mail servers your domain advertises. If the MX points at the wrong host (an old provider, or nothing), no amount of SPF will help — fix the MX first. Compare against what your mail provider told you to set.

2. Can my server actually send/receive? — SMTP & IMAP testers

• The SMTP tester opens a connection to a mail server and checks it accepts mail — it catches wrong hostnames, closed ports (25/465/587) and auth failures.

• The IMAP tester verifies you can log in and list mailboxes — useful when email arrives but a client cannot read it.

If SMTP fails on your own server, it is usually a firewall (port blocked), a not-yet-issued TLS certificate, or authentication rejected — not DNS.

3. Is my domain authorised to send? — SPF, DKIM and DMARC

These are TXT records and they are what stop your mail being treated as spam:

• SPF (v=spf1 ...) lists the servers allowed to send for your domain. Check it with the TXT record checker. Symptoms of a broken SPF: mail from your own domain landing in recipients' spam, or SPF fail in message headers.

• DKIM adds a cryptographic signature that ties a message to your domain. The public key is published as a TXT record; the private key signs on your server. A missing/mismatched pair breaks the signature.

• DMARC (_dmarc) tells receivers what to do when SPF/DKIM fail, and gives you reports. Start with p=none to monitor, then tighten to quarantine or reject.

Full setup: Email DNS: SPF, DKIM and DMARC.

4. Am I blacklisted? — blacklist checkers

Use the email blacklist checker against your sending IP (not the domain). If you appear on a major list, mail is being rejected outright. Blacklists are usually triggered by spam complaints or compromised accounts; removal means fixing the cause, then requesting delisting. A missing or broken SPF/DKIM makes blacklisting far more likely.

5. Are my marketing emails compliant? — List-Unsubscribe checker

The List-Unsubscribe header checker verifies your bulk mail carries the one-click unsubscribe header major providers now expect. Missing it hurts deliverability for newsletters.

Putting it together

Work top to bottom: MX (routing) → SMTP/IMAP (connection) → SPF/DKIM/DMARC (authorisation) → blacklist (reputation) → List-Unsubscribe (compliance). Nine times out of ten the culprit shows up in the first three steps. If you would rather not run mail yourself, our Business Email service handles the DNS and deliverability for you.