Email Deliverability Checker: A Practical Guide to Reading the Results

An email deliverability checker looks up the DNS records that decide whether receiving servers trust mail sent from your domain, then grades them. In practice that means four things: MX (can the domain receive mail), SPF (which servers may send as you), DKIM (is each message cryptographically signed) and DMARC (what should a receiver do when the first two fail, and where should reports go). Those four records are the part of deliverability you can verify in seconds, which is why checkers exist.

They are also easy to over-trust. A checker reads public DNS. It does not see your sending reputation, your complaint rate, your list quality or your content, and it cannot tell you which folder a given message reached. BusinessMCP’s free email deliverability checker says as much on its own page: passing the checks does not guarantee inbox placement. It runs in your browser against Google Public DNS, grades the four records, and shows the exact record to paste when one is missing. It also warns that DKIM selectors are provider-specific, so a miss may mean the tool did not guess your selector rather than that DKIM is broken.

That honesty is the right frame. Treat the grade as a pre-flight checklist. If SPF is missing or broken, fix it before anything else. If everything passes and mail still lands in spam, the cause lives elsewhere, and the articles here walk through where to look.

A sensible reading order:

• Run the test first. Our walkthrough on how to check email deliverability and the notes on what an email deliverability test can and cannot show explain each line of a typical report.
• Fix the records. Follow the SPF, DKIM and DMARC setup steps, then read about SPF permerror and the 10-lookup limit and DKIM selector not found if the checker flags them.
• Meet sender rules. Google and Yahoo changed what bulk senders must do; see the Gmail and Yahoo bulk sender requirements.
• Go beyond DNS. When authentication passes but mail still misses the inbox, start with emails going to spam despite SPF, DKIM and DMARC and how to improve email deliverability.

If you send cold outreach, BusinessMCP’s longer SPF, DKIM and DMARC guide and its cold email deliverability and compliance guide cover the same ground from the sender’s side. We cite them because their rules and thresholds are published and checkable; we also link to Google’s and Yahoo’s own sender documentation wherever we state a requirement.

We are an independent publication. We say what a tool does, who it suits and where it stops, and we expect you to confirm current rules on the providers’ own pages, because mailbox providers change them.