What is the Validity Heatwave blocklist, and how do I check my domain?

What Heatwave lists

Most warm-up tools put your new mailboxes into a pool with other users' mailboxes. The pool sends mail between its members, pulls it out of spam, marks it important and replies, so mailbox providers see engagement on a brand-new domain. Validity calls this synthetic reputation warming, and Heatwave lists the domains that do it.

Validity's lookup shows a classification for each listing. Warming means synthetic warming was observed but no real cold outreach yet. A domain can also be listed as a registered sibling of a warming family: a related domain registered alongside ones that were seen warming, listed before it sends anything.

Why it matters

Practitioners reported more than a million domains listed in the first week, with several thousand added in a single day, and mailbox and security providers including Spamhaus, Proofpoint and Comcast using or testing the signal. A listed domain can lose inbox placement across every campaign it sends, and the domains you spent weeks warming are the ones at risk.

How to check your domains

1. 1

   1. Open the lookup

   Go to lookup.validity.tools and enter the sending domain only: no URL, email address or IP.

2. 2

   2. Read the verdict

   "Not currently listed" means there's no current entry for that exact domain. Lookups are exact-match, so check every sending domain separately, including subdomains.

3. 3

   3. Read the related domains

   The result can show listed domains with similar names. Those are leads, not proof: check whether any of them are yours, or set up by an agency or tool you use.

4. 4

   4. Act on a listing

   Stop sending from a listed domain, move its mailboxes to a fresh domain, and turn off any engagement-pool warm-up on the new one. If you believe the listing is wrong, use Validity's listing review request.

How to warm up without a warm-up pool

1. Let new domains age about 14 days before the first email.
2. Start real sending low: about 2 emails a day per mailbox, to real prospects on a verified list.
3. Ramp slowly to around 30 a day per mailbox over about three weeks, and keep total volume spread across several mailboxes and domains.
4. Brake automatically: slow down or pause a mailbox when bounces, spam placement or complaints rise.
5. Judge every domain on real replies; one that stays under about 1% replies is worth retiring.

This is how ReplyDak warms mailboxes. It has no warm-up pool, and it checks every sending domain against Heatwave and the main blocklists daily, alerting you if one is listed. See the warm-up guide for the full schedule.