Check a Domain for Email Deliverability: The Full Checklist
Check a Domain for Email Deliverability
Checking a domain for email deliverability means verifying its authentication records, reputation, and blacklist status to confirm mail sent from it will reach the inbox.
What to check
Four things, in order: authentication (SPF, DKIM, DMARC set and aligned), blacklist status (is the domain or its IP listed), reputation (complaint and bounce history), and a live spam-score test. A domain that passes all four is set up to deliver. A failure in any one explains a spam problem. Each check has its own tool on the email deliverability testing page, and the wider email deliverability hub explains why the order matters.
How to run the check
Confirm authentication with a checker, run a blacklist lookup, review google postmaster for Gmail reputation, and finish with a spam test email. If the records look right and mail still fails, drop a level: send a test email to see the message as a recipient does, and use an SMTP test to confirm the server is accepting the connection at all.
When placement is bad and the records are clean, run the diagnosis staged: authentication first, then reputation, then content, then the AI-mediated inbox that increasingly sits between a message and its reader. That order comes from George, our CEO, whose Email Marketing Bible ships it as a step-by-step triage, Gemini summaries included.
Running through SPF, DKIM, DMARC and blacklist checks one tool at a time, then remembering to repeat the whole thing after any DNS change, is manual work with no memory. The fix is an AI agent that already knows to check, not a person who has to remember to: describe the domain to Claude, ChatGPT or Cursor, and Nitrosend's MCP server runs the full check as part of setup.
How Nitrosend does it automatically
Every verified sending domain gets a deliverability health object with a single headline state and four data layers, so the domain check is continuous rather than a manual audit. The compliance layer grades it against the 2026 bulk-sender requirements out of the box. Domains carrying transactional email get the same continuous check, which is where it earns the most, and the health state is readable from the email API so a failing domain can be caught in your own code rather than in a dashboard nobody opened.
A useful domain check also runs wider than the four steps above, and ours does: domain verification, DNS health across SPF, DKIM, return path, tracking and DMARC, the physical address, the sender configuration and the campaign preflight, all before anything goes out.
We report a domain reputation score where 1.0 is healthy, and every send is gated on the health of the specific domain it goes out on rather than the account as a whole. I wrote up the mechanics in Sending Email at Scale: if one brand's domain starts bouncing, that domain gets throttled or held while other brands keep sending on their own clean domains.
Underneath that sit spam-rate and per-provider placement trends, DNSBL monitoring through Spamhaus DQS, and degradation alerts gated by hysteresis, so one bad day does not fire a false alarm.
FAQ
How do I check a domain for email deliverability?
Verify its SPF, DKIM, and DMARC, check it against blacklists, review its reputation, and run a spam-score test. Passing all four means the domain is set up to deliver.
What makes a domain deliverable?
Aligned authentication, a clean blacklist status, a low complaint and bounce history, and content that doesn't trip spam filters.