Free tool
Domain health check: blacklists, SPF, DKIM, DMARC and domain age
Enter a domain to check its email health in one report: SPF, DKIM, DMARC and MX records, the domain and the IPs of its mail servers against free DNS blocklists, and the domain's registration and expiry dates. Each finding says what breaks and how to fix it.
A healthy sending domain has one valid SPF record, a DKIM key, a DMARC policy, MX records, no blocklist listings and a registration that does not expire soon. The lookups run in your browser; nothing is stored.
DNS and blocklist lookups go from your browser to Cloudflare's public DNS resolver, the registration date to the domain registry. A full check takes a few seconds.
How it works
How to read the report
The four numbers on top count errors, warnings, blocklist hits and the domain's age. Each part of the report then shows its worst finding. Error: fix it before you send. Warning: fix it soon or confirm it by hand. Note: read it and decide.
- SPF, DKIM, DMARC and MX: the same rules as the SPF, DKIM and DMARC checker, which explains every finding; Gmail and Yahoo require all three records from bulk senders (what cold email domains need)
- A blocklist hit on the domain (error): receivers that use the list score every email that carries the domain, in the From address or in a link; stop the source, then ask the list for removal
- A hit on an IP from your SPF record: that server sends as your domain; on a shared IP, ask your provider; on your own server, find the compromised account or form first
- A hit on an MX IP: that server receives your mail; it matters when the same server also sends, so tell your mailbox provider
- Registered less than 14 days ago (warning): a new domain has no sending history; warm up its mailboxes for 14 days before the first cold email (how long warm-up takes)
- Expires within 30 days (warning) or expired (error): an expired domain stops its mailboxes and its redirect; turn on auto-renew
- Every check passes and mail still lands in spam: the cause is usually the copy, the volume or the list; what to check before you replace a burned domain has the tests
Background
Which blocklists the checker queries
The checker queries SpamCop, PSBL, UCEPROTECT level 1, NordSpam, s5h.net and 0spam for IPs, and the NordSpam domain list for the domain. Their published terms allow free DNS queries, and they answer correctly through a public resolver. Before every check it queries each list's test entry; a list that does not answer is reported as not checked, so a missing answer never reads as clean.
Spamhaus, Barracuda, SURBL and URIBL are left out. Spamhaus answers public resolvers with a refusal code, Barracuda answers only registered DNS servers, SURBL's free service may not be built into other services and URIBL refuses public resolvers. The report links each one's own lookup page; check the domain there by hand.
A listing is a reason to look closer. It does not prove a placement drop on its own: Gmail and Outlook rely on their own reputation data, which Google Postmaster Tools and SNDS show. The email domain reputation checkers compared post covers those, and the blacklist check skill runs the lookups in Claude or ChatGPT through your own resolver.
Background
Domain age and cold email
Google's sender guidelines and Yahoo's sender requirements set no minimum domain age. What a new domain lacks is sending history, which warm-up builds: 14 days of warm-up before the first cold email, then volume rises over about a week. Domains for cold email covers how to pick, buy and set them up.
An older domain bought secondhand comes with a history you did not create. Run it through this check and Google Safe Browsing before you put mailboxes on it.
Free guide19 min read
Send 100,000 cold emails a month
Domains and mailboxes you need, DNS, warm-up, lists, copy and follow-ups, with a launch checklist, sent to your inbox.
Questions
How do I check if my domain is blacklisted?
Enter the domain above. The checker looks the domain up on the NordSpam domain list and the IPs of its mail servers on six IP blocklists, and links the Spamhaus, Barracuda, SURBL and URIBL lookup pages for the lists it does not query.
Why doesn't the checker query Spamhaus?
Spamhaus refuses queries that come through public resolvers such as Cloudflare or Google DNS and answers them with a refusal code, so a browser tool cannot read a real result. Use the Spamhaus lookup page, or query from your own mail server's resolver.
What is a good domain reputation for cold email?
No blocklist listings, SPF, DKIM and DMARC passing, a spam rate in Google Postmaster Tools below 0.1% (Google asks senders never to reach 0.3%), and replies coming in. This check covers the DNS and blocklist part; the complaint rate and placement need Postmaster Tools and a placement test.
How old should a domain be before I send cold email?
Gmail and Yahoo set no minimum age. Warm up new mailboxes for 14 days before the first cold email and raise volume over the following week.
Does this tool store the domains I check?
No. DNS and blocklist lookups go from your browser to Cloudflare's public DNS resolver and the registration date to the domain's registry. We do not receive the domain or the result unless you ask us to email the fixes.
In your AI assistant
Run the same checks in Claude or ChatGPT
Free SKILL.md files with the rules behind this tool. Install them in Claude or Claude Code, or paste them into ChatGPT, Gemini, Grok or Cursor.
Mailboxes, warm-up and sending in one place
$2.50 a mailbox a month. DNS records are set for you, and every mailbox shows its warm-up numbers from day one.
Deliverability call
Talk to our deliverability team
Book a call with the people who run our mailbox infrastructure. We look at your current setup and tell you what to change.
- Review your domains, DNS records and current inbox placement
- Size the setup: domains, mailboxes per domain and daily volume per mailbox
- Plan warm-up and the move from your current provider or sequencer
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