What is Heatwave?

New: launched 3 September 2026.

Heatwave checks sending domains, and Validity runs it. Our free checker cannot see this list, so use Heatwave's own free lookup.

What the operator says

"A real-time domain blocklist focused on cold email infrastructure." Validity, About Heatwave, read 1 Nov 2026.

Why it exists

A new domain has no history, so mailbox providers go slowly and watch how real people react. Warm-up services sell a way round that wait: a pool of automated mailboxes that open, reply to and rescue each other's mail. Heatwave was built to spot that fake engagement, signals no real reader made.

What it really measures

Heatwave is aimed at cold email senders using those services, and at the campaigns that follow. Scoring looks at things like templated content, shared personas, freshly registered domains and known cold email infrastructure.

It judges the domain, not the IP, so moving to another sending server changes nothing here.

It can reach domains that have not sent yet. When Validity identifies a family of domains run together for warm-up,
other domains in that family can be listed before any mail is seen from them. Validity calls this pre-warming. So a spare
domain bought for the same outreach can already be on the list.

Validity says warming services often register domains that resemble the customer's own. Searching your main domain on the
lookup can show related ones you never knew existed.

A warmed domain later seen sending real cold campaigns also gets an active-outreach status on top of its listing.

Why you might be there

These services often get switched on without the owner hearing about it, so ask around first:

• Has anyone in sales, marketing or revenue operations switched on a warm-up or outreach service?
• Has an agency or outside vendor done it for you?
• Does the lookup show related domains of yours as listed?

If you are sure none of that happened, a wrong call is still possible: a mistaken classification, impersonation, a compromised domain, or two unrelated domains confused.

What to think about

• A warm-up listing stays on record, so stopping does not clear it. On most lists, you fix the cause and then ask for removal. Here the listing is a record of what was seen. Stop anyway, because the active-outreach status can change when the outreach ends.
• What it costs you depends on who receives your mail. Each receiver decides what to do with it, and each mailbox provider treats a domain blocklist differently. Validity says the list is used or being evaluated by partners including Comcast, Spamhaus and SURBL, which does not mean they block on it. Microsoft does use Validity data, though Validity does not name Microsoft among Heatwave's users.
• A clean result only means this list has not flagged that exact domain. A subdomain is judged on its own.

How to get off it

The one route is a listing review, and it only removes a listing that was wrong.

• It must come from someone authorised, using their own named address at that domain. Role addresses like info@ or sales@ are refused.
• Give your reasons and specific supporting information on why the original call was wrong or wrongly attributed. Screenshots are optional.
• People handle it, typically in 2 to 5 business days.
• A pre-warming listing can also drop off by itself if Validity takes the domain out of that family.

If the listing is accurate, there is no way off it. Validity's advice is to stop using the warming service and ramp with real, permissioned recipients, though that does not clear the listing. Talk to us on the SOS Hotline before you decide what to do with the domain.

Not sure what this means for you? Ask a person on our free SOS Hotline. Tell us the list and the IP or domain, and we reply within 48 to 72 hours.