Validity Heatwave blocklist: “synthetic reputation warming observed”

Short answer: Your domain is on Validity's Heatwave blocklist, which flags domains seen in synthetic warm-up networks or cold outreach. Check it at lookup.validity.tools. Listings don't expire and stopping warm-up doesn't remove them: only a review that finds the listing was wrong does.

The listing notice looks like this
Listed · Warming: Synthetic reputation warming observed
DNS answer 127.0.95.2 · listing score 95/100 · does not expire merely because the activity later stops

What it means

Heatwave is a domain blocklist that Validity launched on 3 September 2026. It lists sending domains, not IP addresses, that Validity's data shows taking part in synthetic warming: warm-up tools that trade automated messages and fake engagement between mailboxes they control. Active outreach is added when the domain is also seen sending live cold campaigns, and pre-warming marks registered domains of the same operator before they send. Validity names Comcast, Proofpoint, Spamhaus, SURBL and some ESPs as users or evaluators, and each decides for itself whether to filter mail from listed domains. So there is no standard bounce: you usually notice it as mail going to spam or an email service questioning your account. A warming listing is a permanent record of what was observed.

How to fix it

  1. Look up the exact domain at lookup.validity.tools (free, 100 checks a day). Subdomains are listed separately, and searching your main domain can show related domains tied to it.
  2. Stop warm-up services on every domain you send from. Stopping doesn't remove a listing, but domains that keep warming can be listed next.
  3. If the listing is wrong (an agency, vendor or ex-employee used the domain without approval, or it was impersonated or compromised), request a review at lookup.validity.tools/delist.
  4. The request must come from your own named address at the listed domain (not info@, sales@ or support@) and explain why the original listing was wrong. Validity answers in 2–5 business days; if it agrees, the listing is removed.
  5. If the listing is accurate, a review won't remove it, and Validity says changing how you send doesn't undo an accurate listing. From now on, send from that domain only to people who asked for your mail.
  6. Check the domain below: SPF, DKIM and DMARC still have to pass for any of your mail to reach the inbox.

Check your domain now

After the fix, send a test email to see SPF, DKIM and DMARC pass on a real message, then keep an eye on it: free DMARC monitoring shows every service that sends mail as your domain and which ones fail, in plain English.

Rather not touch DNS? I set up SPF, DKIM and DMARC without breaking your other senders, with a before/after report.

Get it fixed on Fiverr

Prefer to do it yourself? Get the step-by-step Fix Kit ($15) – 28-page guide, checklist, 20+ providers.

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