Find sending domains
How it works
Patterns are generated
Prefixes, suffixes and hyphenated forms that read naturally in a From: address, crossed with the TLDs you tick.
Each is queried for NS and SOA
A name with no zone at all returns NXDOMAIN from the resolver. That is the strongest availability signal DNS can give.
Results are sorted
Likely-available names first, with registrar search links so you can confirm and buy in one step.
You check history
Before buying anything that has been registered before, run it through the domain age checker — a dropped domain can carry a blacklist entry.
Why secondary domains exist
Cold email is a numbers activity with a failure mode: any domain that sends enough of it will eventually pick up complaints, and complaints damage the reputation of the domain, not the mailbox. If that domain is also the one your invoices, support replies and password resets come from, a bad campaign becomes a business problem. Secondary domains isolate the risk. The primary domain stays clean; the outreach domains are cheap and replaceable.
The convention is to pick names close enough to the brand that a reply feels natural — tryacme.com, acmehq.co, getacme.net — and to redirect each one to the main site so anyone who checks lands somewhere real. Three to five inboxes per domain, thirty or so sends per inbox per day, and a fleet of domains sized to the volume you need. The capacity calculator does that arithmetic.
What “likely available” means here
The tool asks a public resolver for the NS and SOA records of every candidate. A registered domain almost always has a zone with nameservers; an unregistered one returns NXDOMAIN because nothing exists above it in the registry's zone. That is a strong signal but not proof — a small number of registered domains are parked without DNS, and some registries return odd answers for reserved names. The registrar links are there to confirm before you plan around a name.
Names to avoid
Anything that is a typo of a brand you do not own. It is a trademark problem and receivers treat lookalikes of well-known names as phishing signals.
TLDs with a spam history. .xyz, .top, .click and their relatives are cheap for a reason. Filters weight them negatively before you have sent a single message. Stick to .com, .co, .net, .io and .org unless there is a specific reason not to.
Dropped domains without checking. A name that was registered and abandoned may still be on a blacklist or carry a reputation from its previous owner. Run any candidate that shows a registration history through the domain age checker and the blacklist checker before buying.
After you buy
Set up the redirect to your main site, publish SPF, DKIM and DMARC, and let the domain sit for a couple of weeks before the first inbox goes live. Domains registered and sending on the same day look exactly like what they are. The warmup calculator covers the ramp from there.
Frequently asked questions
How many secondary domains do I need?
Divide your daily send target by about ninety — three inboxes at thirty a day per domain. Twenty domains carries roughly 1,800 sends a day. The capacity calculator does this with your own numbers.
Should secondary domains match the brand exactly?
Close is better than exact. tryacme.com or acmehq.co reads as a legitimate variant; acme-outreach-mail.biz reads as a spam operation. Recipients do look at the domain.
Which TLD is best for cold email?
.com first, then .co and .net. .io and .org are fine for technology and non-profit contexts. Avoid the cheap TLDs entirely — the reputation penalty costs more than the registration saving.
Does the availability check reserve the domain?
No. It reads public DNS only. Nothing you type reaches a server of mine, and no registrar is queried until you click through.
A domain shows as available but the registrar says it is taken. Why?
It has a registration but no DNS zone — parked with no nameservers, or in a post-expiry grace period. The registrar's answer is authoritative.
Can I reuse a domain that was burned?
Rarely worth it. Reputation on a sending domain decays slowly and blacklist entries can persist for months. A fresh domain costs a few dollars and starts clean.
Last reviewed
What to run next
The checks that most often follow this one.
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Guides that go deeper
When the tools tell you something is wrong
The diagnostics here are free and always will be. When the fix is bigger than a DNS record, this is the work I do.
Deliverability rescue
Mail landing in spam, replies gone quiet, or a domain suddenly blocked. I find the actual cause rather than guessing, and fix it.
- Authentication and alignment failures
- Blocklist delistings and reputation repair
- Gateway and filter-level blocks
- A written report on what broke and why
Email & sending infrastructure
Sending domains, inboxes, authentication and warmup, built to survive volume instead of burning down in a month.
- Domain and inbox fleets at any scale
- SPF, DKIM, DMARC and tracking domains
- Google Workspace and Microsoft 365 inboxes
- Handover documentation you actually own
Domain, DNS & migration
Changing registrar, mail provider or host without a day of downtime or a week of mail silently failing.
- Registrar and nameserver moves
- Workspace and Microsoft 365 migrations
- MX, SSL and subdomain cutover
- Staged rollout with rollback at every step
Monitoring & retainer
Infrastructure drifts. Records get edited, certificates expire, domains get listed. Ongoing eyes on the fleet.
- Scheduled checks across every domain
- Alerts before your clients notice
- Monthly reporting
- Priority response when something breaks
Start with a call
Bring a domain and the symptom. I will tell you what is actually wrong and whether you need me at all — plenty of people leave that call able to fix it themselves.
Thirty minutes, no pitch
We will run the checks together on your actual domains, and you will leave knowing what is broken, what it takes to fix, and what it should cost. If that is a job you can do in-house, I will say so.