Email deliverability checker

How to use it

Type the domain in your From address (for jane@acme.com, that is acme.com). You can also paste an email address or a website URL; the checker extracts the domain. If you send from a subdomain such as mail.acme.com, check that subdomain.

What each record does

MX: where mail for the domain is delivered

MX records name the servers that receive email for your domain. They are not needed to send, but a domain that cannot receive replies looks suspicious to receivers, and replies to your outreach will go nowhere. The checker also names the provider when it recognizes the host (Google Workspace, Microsoft 365 and others).

SPF: which servers may send as you

SPF is a single TXT record beginning v=spf1 that lists the servers and services allowed to send mail for the domain. Common problems: more than one SPF record (which makes SPF fail outright), ending with +all (which authorizes everyone), and too many includes, which pushes past the 10-lookup limit in the SPF standard. End the record with ~all or -all.

DKIM: a signature that proves the message is yours

DKIM adds a cryptographic signature to each message, verified against a public key published at selector._domainkey.yourdomain. Your email provider generates the key; you publish it. Use a 2048-bit key where your provider supports it. An empty key (p=) means the key was revoked.

DMARC: what to do when checks fail, and who to tell

DMARC, published at _dmarc.yourdomain, tells receivers what to do with mail that fails both SPF and DKIM alignment — p=none (deliver and report), p=quarantine (spam folder) or p=reject — and where to send aggregate reports (rua=). Those reports show every service sending as your domain, which is how you find out what to fix before you tighten the policy.

Google and Yahoo sender requirements

Since February 2024, Google and Yahoo have published requirements for anyone sending to their users. According to Google's email sender guidelines and Yahoo's sender best practices, all senders need SPF or DKIM and should keep their spam rate low. Bulk senders (Google's threshold is around 5,000 messages a day to Gmail addresses) must also:

• authenticate with both SPF and DKIM;
• publish a DMARC record with at least p=none, with the From domain aligned to SPF or DKIM;
• offer one-click unsubscribe (RFC 8058) on marketing and subscribed messages, and honor it promptly;
• keep the spam complaint rate reported in Google Postmaster Tools below 0.3%.

DNS can show the first two. The last two depend on your sending tool and your recipients, so the checker lists them without a verdict. The requirements change from time to time; the providers' pages above are the authority.

Fixing problems safely

• Change one record at a time and re-check after the TTL expires.
• Merge SPF records rather than adding a second one.
• Start DMARC at p=none with a reporting address, read the reports for a few weeks, then tighten.
• When you stop using a sending service, remove its SPF include and DKIM record.

Once authentication is in place, check the message itself with the spam word checker, and read common email deliverability mistakes.