How we set up a cold email sending domain

We set up every cold email sending domain in the same order, and each step exists because skipping it costs us something later. The order is name, mail records, website, mailboxes, warmup, and signatures. Nearly all of the work happens before the first email goes out.

How do we choose a sending domain name?

We pick names made of category or topic words, not the client's brand with a prefix like get or try. This is the default for every program, so we no longer debate it for each new order.

The reason came from a blacklist incident in late October 2026, when 62 domains across six programs were listed in one window. A later review found that the listed domains were prefix-plus-brand names registered in same-day batches. That pattern ties a brand's domains together, so they get listed together.

We also ask the seller to register our domains across several days and several registrars, never in one batch. You can read more about how listings work on our sending domain blacklists page.

Which mail records does a new domain need?

Every sending domain needs SPF, DKIM, and DMARC. SPF says which servers may send for the domain, DKIM signs each message, and DMARC tells receivers what to do when those checks fail. Our health check marks a domain red when SPF or DMARC is missing, and yellow when DKIM is missing or the DMARC policy is set to none.

DKIM is the record that trips people up, because the name it lives under depends on the mailbox provider. Google uses one name, Microsoft uses selector1 and selector2, and some managed setups use a plain dkim name. We check a list of names instead of one, since a good record can sit under a name we didn't look for.

We also check where the DMARC reports go. Some providers point a new domain's report address at its first sending mailbox, which means one report per receiver per day lands in the sending inbox. One program had 1,355 of those reports in its sending tool before we moved the address and kept the policy as it was. We also keep a domain check page for looking at a domain's records.

Why does the domain show the real company website?

A prospect who types the sending domain into a browser should land on the company that emailed them. We looked into this in October 2026 after a prospect hit a dead domain.

A redirect moves the visitor to the client's site, so the address bar changes. Masking shows the client's site on the sending domain, so the address bar stays put. Our standard today is masking, and we confirm each domain by loading it and reading the page title.

We don't claim this helps inbox placement. Gmail's sender guidelines and Microsoft's 2025 rules don't mention website redirects, and the vendors who say otherwise give no data. A masked page also still links to the client's main domain many times, so it doesn't hide the relationship, and we choose based on what the visitor sees.

Checking by title matters because a status of masking active only means the proxy is set up. Some client sites also use bot protection that blocks the proxy, and the visitor then sees a 403 page instead of the company site.

How many mailboxes go on each domain?

We put two to three Google mailboxes on each domain. What we've heard burns a domain is hundreds of mailboxes on one domain, about 10% bounces, and missing authentication records. We keep the count low and the records complete. We break down what a full setup costs on our infrastructure cost page.

How long does a new domain warm up?

A new mailbox warms up for 30 days before it joins any active sending batch. Cold sending from a fresh mailbox tanks deliverability and burns the domain right away. We hold every mailbox for the full 30 days.

We enforce the rule at two points in our rotation system. A domain only enters the sending pool once one of its mailboxes is 30 days old, and any mailbox under 30 days stays out of the active group. Our health check also skips a domain younger than 30 days entirely, since its reputation signals are noise before we send from it.

After warmup, each client's domains run in three batches, and two batches send while the third rests. About a third of the mailboxes sit idle at any moment by design, because the rest period is what protects reputation.

What signature goes on each mailbox?

Every mailbox uses our standard signature with four spintax versions. New mailboxes arrive with a blank signature, so after we add a batch we copy the sender's live signature onto each new mailbox.

We never put a clickable domain in a signature. A bare domain turns into a link on its own, and a link breaks one of our deliverability rules, so we write the domain with a space before the dot.

Common questions