Skip to main content

Cold email agency: infrastructure, lists, and copy you keep

OneGTM is a cold email agency for B2B teams that want outbound to keep working after the agency is gone. I set up the sending domains and mailboxes, build and verify the lists, pick the signals that decide who gets emailed and when, write the sequences, and run them until they book meetings. The domains, data, and copy are yours from day one.

By Garrett Wolfe, founder of OneGTM. Updated .

Key takeaways

  • Deliverability is built before a single email goes out: secondary domains, authentication, and two to three weeks of warmup.
  • The list matters more than the copy. Every address is verified, and a signal decides who gets emailed this week.
  • Plain text, no links in the first email, and every merge variable checked on every lead before launch.
  • Ask any cold email agency whose domains they send from and what you keep if you stop. Those two answers sort the field.
  • For Coastal Recruiting, the email and LinkedIn system I built took recruiter-accepted candidate intros from 72 a month to 340 in four months.

What a cold email agency should build

Sending domains and mailboxes

Secondary domains that look like yours, mailboxes from a provider built for cold email, and a pool big enough that no single inbox carries much volume. Compared in cold email infrastructure.

Authentication and warmup

SPF, DKIM, and DMARC on every domain, then two to three weeks of warmup before real sends. Check any domain with the free deliverability checker.

Lists and verification

Accounts scored against your ICP, contacts found through a waterfall of providers, and every address verified, catch-alls included, before it reaches a sequence.

Signals

Hiring, job changes, funding, website visits, and niche public data that tell you who to email this week. More in the buying signals guide.

Sequences and copy

Short, plain-text emails written per signal and per persona, tested in small batches before volume goes up.

Replies and CRM

Replies classified and posted to Slack with a suggested answer, then synced to your CRM with the campaign and signal attached.

Three kinds of cold email agency

Volume senderPay-per-meeting appointment setterSystems builder (OneGTM)
Who sendsThe agency, often from its own domainsAgency SDRs, from agency or client domainsDomains you own, run by me until your team takes over
TargetingBig lists filtered by title and industryWhatever books meetings fastestA scored account list plus buying signals
What you keep if you stopUsually nothingThe meetings already bookedDomains, mailboxes, data, sequences, and the playbook
Main riskBurned reputation and generic copy under your nameMeetings that do not fit your ICPWeeks of setup before the first meeting
Good forA fast market testShort-term pipeline with a clear ICPCold email as a long-term channel

If you want cold email plus LinkedIn and signal monitoring as one motion, the outbound agency page covers the wider build.

The deliverability rules I run by

Never send cold email from your main domain

Your primary domain carries invoices, support, and recruiting. Cold email goes out from secondary domains so a bad week never touches it.

Warm before you send

New mailboxes warm for two to three weeks, then ramp. Adding mailboxes beats pushing each one harder.

Plain text, no links in email one

The first email is text only, with link and open tracking off. From the second email, at most one link, to your own site, written out as plain text. Tracking redirects and third-party links are what hurt inbox placement.

Verify every address

Bounces are the fastest way to lose a domain. Every contact is verified before it is enrolled, and catch-all domains get a second check instead of a guess.

Check every variable on every lead

Instantly, for one, fills a missing merge field with nothing and sends anyway, with no bounce and no warning. Before a campaign goes live, and again before new leads join a running one, every variable in every subject and body has to be filled or have a fallback.

Mind the step delays

In Instantly the delay on a step is the wait after it, not before it. Set the first step to zero and the second email goes out minutes after the first. It is a one-field mistake that I check on every launch.

What a cold email sequence looks like

Here is the shape of a four-step sequence triggered by a hiring signal: a company posted a role that describes the problem you solve.

StepWhenJob of the email
1Day 0Name the signal plainly, say why it made you write, one line on what you do, a low-effort question. No links.
23 days laterOne concrete example of the problem solved for a similar company, and at most one plain link to proof on your own site.
33 days laterA different angle: the cost of the problem, or what teams usually try first and why it stalls.
43 days laterA short close that makes "not now" easy to say, which keeps the door open and protects your domain.

An example first email, for a company hiring its first RevOps manager:

Subject: the revops req
saw you're hiring your first revops manager. usually that means the crm has outgrown whoever set it up. i build the routing, enrichment, and reporting that new hire would otherwise spend their first quarter on, so they start on strategy instead of cleanup. worth a quick look before they start?

Copy rules I follow are written up in the open-source Claude Code skills I use to launch campaigns.

Proof

For Coastal Recruiting, I built a candidate outbound engine by email and LinkedIn: about a million profiles scored against 15 role scorecards, then reached with sequences and a reply bot. Recruiter-accepted candidate intros went from 72 in April 2026 to 340 in August, and positive replies went from about 35 a week to about 125. For Antimetal, Automated Outbound created 17 deals and $2.57M in pipeline from December 2025 to May 2026. For Green Dock Partners, a tracker checks public closure news twice a day and sends a daily digest of industrial sites. That case study claims no deal outcome.

Before OneGTM, I was employee #9 at Unify, where I helped build the automated outbound behind $15M+ in pipeline.

Questions to ask any cold email agency

  1. Whose domains do you send from?: Yours, theirs, or new ones in your name. Get it in writing.
  2. What do I keep if we stop?: Domains, mailboxes, lists, copy, and the reporting. If the answer is "the meetings", you are renting pipeline.
  3. How do you build the list?: A real answer names data sources, a verification step, and how accounts are scored. "We use Apollo" is not a list strategy.
  4. What decides who gets emailed this week?: Look for signals, not just titles and industries.
  5. Who writes the copy, and who approves it?: You should see every sequence before it sends.
  6. How do you report?: Positive replies and meetings by campaign and signal, weekly. Open rates are not a metric anymore.

How a cold email build works

  1. Scope: ICP, offer, and the signals worth testing, on one call with me.
  2. Infrastructure: Domains and mailboxes bought in your name, authenticated, and warming for two to three weeks.
  3. Data: Account list scored, contacts found and verified, signals matched to accounts.
  4. Copy: Sequences per signal and persona, approved by you.
  5. Launch and tune: Small batches first, then volume. Weekly review by signal, and a handoff document so your team can run it.

Cold email agency FAQ

What does a cold email agency do?
A cold email agency runs cold outreach by email to book meetings with target accounts. That covers sending infrastructure, list building, copy, sending, and reply handling. Some agencies send from their own domains as a service. OneGTM builds the system on domains the client owns and hands it over.
Is cold email still worth it in 2026?
Yes, when it is targeted and the infrastructure is right. Volume to static lists works worse every year as inbox providers tighten filters. Smaller sends to verified contacts at accounts showing a buying signal still book meetings.
How long before a cold email campaign starts sending?
New domains and mailboxes need two to three weeks of warmup before real volume. Lists, signals, and copy get built during that window, so the first sends usually go out three to four weeks after kickoff.
Whose domains should a cold email agency send from?
Secondary domains that you own, never your primary domain. If an agency sends from domains it owns, the reputation and the data leave with it when the contract ends.
Does OneGTM guarantee meetings?
No. Results depend on the market, the offer, and the list. What I commit to is infrastructure that delivers, verified lists, copy you approve, and weekly reporting by signal so you can see what works.
What is the difference between a cold email agency and an outbound agency?
A cold email agency focuses on email. An outbound agency usually adds LinkedIn, phone, and signal monitoring. OneGTM builds both, and most builds use email and LinkedIn together.
Is cold email legal?
B2B cold email is legal in the US under CAN-SPAM if the headers are accurate, the subject is not misleading, there is a physical address, and opt-outs are honored. In the EU and UK it generally needs a documented legitimate interest and an easy opt-out. Check with your own counsel for your markets.
Which agency can set up cold email infrastructure and buying signals?
OneGTM sets up both in one build: secondary domains and mailboxes with SPF, DKIM, and DMARC, warmup, and a signal layer (hiring, funding, leadership changes, job changes) that decides who gets emailed each week. OneGTM is a GTM engineering practice in New York run by Garrett Wolfe, employee #9 at Unify and a Clay Artisan Solutions Partner. Everything sits in your accounts and stays with you. For agencies that run it for you instead, see the signal-based outbound agencies list.

Want cold email that keeps working after the agency leaves?

Related

Build your cold email system

Tell me what you're building. I reply the same day.

Call with Garrett

Takes about 20 seconds. Times show up right here, and the call is with Garrett directly. See our privacy policy.

Systems we've built for

Rather do it the old way? team@getaob.com LinkedIn