Run your domain through Spamhaus's lookup at check.spamhaus.org and a multi-list checker, then look at the domains inside your email's links and signature. Ten minutes. If nothing is listed, and for most small senders nothing is, then your problem is a private reputation score that no lookup shows, and the fix is different. Telling those two cases apart is the most useful thing in this article.

Listed versus landing in spam

A blocklist is a public list of domains or IP addresses that receiving servers consult. If you're on one, mail gets refused outright, and the bounce usually names the list. Landing in the spam folder is something else. Gmail, Outlook and Yahoo score senders with their own private reputation systems. Google's sender guidelines don't describe a blocklist at all. They describe a reputation that falls when users report your mail as spam, and they say to keep the spam rate in Postmaster Tools under 0.10% and never reach 0.30%.

So the first question is what you saw. Bounces that mention a list or a "blacklist": check the lists. Mail that delivers but goes to spam: skip to the section on not being listed. A mix, where some companies bounce and others deliver: do both.

Where to check a domain and an IP

  1. Spamhaus: enter your domain at check.spamhaus.org. Spamhaus's Domain Blocklist lists domains only, no IP addresses, and covers domains used for spam, phishing, malware, and legitimate sites that have been compromised.
  2. A multi-list checker, such as the blacklist check on MXToolbox. Enter the domain, and again the sending IP if you know it. It queries many lists at once and reports hits.
  3. The domain behind your links. This is the one people skip. If your signature or email includes a link to your website, receivers check that domain too. Run your website's domain through the same tools.

One point simplifies this if you send through Google. Your mail leaves from Google's servers, so the IP address belongs to Google and isn't yours to check or fix. Only the domains matter: your sending domain and your link domains. If you send through your own server or a separate mail service, check the IP as well.

Reading what you find

Write down the list name, whether the entry is a domain or an IP, and the reason code. Three outcomes:

  • Nothing listed. Good. Skip to "When you are not listed."
  • Listed on Spamhaus. Serious, because large receivers use it. Fix before sending anything else.
  • Listed on a small or obscure list. Often matters little, because most big receivers don't consult it. Fix if it's quick, but don't panic.

Hugo is a garden designer with a small website and a sender domain to match. 12 of his 40 outreach emails were rejected with a line mentioning a domain blocklist. The other 28 delivered. His sending domain checked clean, but his website domain, which was in his signature, was listed. The reason was the part that surprised him: Spamhaus puts compromised legitimate sites in their own category. A plugin on his site had been exploited and was serving spam links. The bounces came from receivers that scan the links in a message.

Getting delisted: what works

Fix the cause first, because a listing returns if the cause remains. For a compromised website that means updating or removing the plugin, changing passwords and asking your host to scan. For a sending domain it means stopping whatever sent the problem mail, whether that was a forged sender, a bad list or a hacked mailbox. Then request removal through the list's own process. Spamhaus states there is never a charge for removing a listing and that anyone offering to remove one for a fee is a scam. It also says most listings drop off on their own once the domain stops matching the criteria. Hugo cleaned the plugin on a Thursday, asked for review on Friday, and got a clean lookup the following week. Timing varies by list, so don't promise yourself a day.

When you are not listed at all

This is the usual result. If the mail goes to spam and the lookups are clean, look at the things receivers actually weigh:

  1. Authentication. Send a test to your own Gmail and open Show original: SPF, DKIM and DMARC should all say PASS. If they don't, DMARC fail: what it means and how to fix it is the next stop.
  2. Volume history. A new domain that sent 80 emails on day one has no record to stand on. Warming up a Gmail account covers the ramp.
  3. Complaints. A handful of spam reports among a few hundred emails is a rate far above Google's 0.30% line, even though the volume is small.
  4. Links and content. Shorteners, tracking redirects and many links all count against you, as in your message has been blocked in Gmail.
  5. List quality. Bounces from guessed addresses hurt. See the bounce rate guide.

Postmaster Tools will show your domain's reputation if you send enough to Gmail users, but at 30 emails a day it will likely show little. Treat an empty chart as no information.

Prevention for a new sender

Send from a domain you can afford to lose, authenticate it before the first send, start at 20 or so emails a day, use verified addresses, keep emails plain with one link or none, and make it easy to opt out so people don't reach for the spam button. Whether to use your main domain at all is covered in can you send cold email from your main domain. The records are in our SPF, DKIM and DMARC guide and the bigger picture is in deliverability basics.

Re-check after a fix

Run the same three lookups two days after the fix and again a week later, and keep a short log: date, tool, result. Then send a small batch of 20 to confirm bounces have stopped. If a listing came back, something is still sending, so look again at the website, the mailboxes and any tool that has access to your domain.

Reputation is slow to build and fast to lose, which is why a steady, modest pace beats a burst. Rocketship finds the buyers, emails them from your own Gmail, follows up, and books the meeting on its own, within a daily limit for each inbox. Plans that get you customers start at $24.99 a month (Launch), and every monthly plan starts with a 7-day free trial, card required. See how the AI workers run outreach.