Ask who owns the domains and mailboxes when the engagement ends, how many emails each mailbox sends per day, and how opt-outs are handled. Those three answers tell you more than any case study, because they reveal whether the agency is building you an asset or renting you one.
Published by emailcampaign.ai. We sell infrastructure to agencies and to teams running outbound in house, so we benefit either way. The ownership question below is the one we would ask.
The three questions
Who owns the domains and mailboxes afterwards? This is the one that decides whether you have bought anything. If the agency registers the domains in their own name, the sending reputation you paid three weeks of warm-up to build stays with them when you leave. You start again from zero somewhere else. Get the answer in writing, and prefer domains registered to you from day one.
How many emails per mailbox per day? The sustainable figure is eight to ten. An agency quoting fifty or a hundred per mailbox is describing a short-lived setup, and the consequence lands on domains that may be yours. Volume should come from more mailboxes, not busier ones, so a large programme should have a mailbox count to match.
What happens when someone opts out? Ask how fast, and whether suppression persists across campaigns and across clients. A decline recorded in one campaign and then reimported three months later is how complaints happen, and complaint rate is the metric that damages a domain. Google publishes the threshold at below 0.1 percent, never reaching 0.3.
How they charge
| Model | How it works | What to watch |
|---|---|---|
| Monthly retainer | Flat fee for campaign management | Whether infrastructure is included or passed through |
| Retainer plus per meeting | Lower base, fee per booked meeting | How a meeting is defined, and who decides it qualified |
| Pay per meeting only | No base fee | Incentive to book meetings that are not qualified |
| Percentage of pipeline | Fee tied to opportunity value | Attribution disputes, and long measurement periods |
Infrastructure is the line most often glossed over. A hundred Google Workspace mailboxes is roughly $840 a month before anyone writes a campaign, plus domains. Ask whether that sits inside the retainer or arrives as a separate bill, because it changes the comparison between quotes substantially.
Red flags
- Guaranteed meeting counts. Nobody controls whether strangers reply. A guarantee is either priced so the agency cannot lose, or it will be met by booking meetings that are not real.
- Evasiveness about domain ownership. There is no good reason for this to be a complicated answer.
- High per-mailbox volume. Anything above roughly twenty a day is borrowing against the domain’s future.
- Vague data sourcing. If they cannot say where records come from, you cannot assess the list and neither can they.
- Reporting that leads with open rate. Open rate has been partly machine generated since Apple Mail Privacy Protection launched in 2021. An agency building its reporting around it is either behind or choosing a flattering number.
What good reporting contains
Replies split into positive, negative and opt-out. Meetings booked. Hard bounce rate, separated from soft. Complaint rate if available. Sends per mailbox per day. Anything else is secondary, and a dashboard that leads with opens and clicks is measuring the two least reliable numbers available.
Agency or in house
An agency is the right call when you want to test whether outbound works for you before committing headcount, or when you need it running before you could hire. Both are legitimate and common.
In house makes sense once outbound is a permanent channel, because the domains, the warmed mailboxes and the sending reputation are assets that take weeks to build and should not sit in someone else’s account. The middle path many teams take is an agency running campaigns on infrastructure the client owns, which keeps the expertise flexible and the asset yours.
Questions, answered straight
- How do I hire a cold email agency?
- Judge them on three answers: who owns the sending domains when the engagement ends, how many emails per mailbox per day they send, and what their opt-out and suppression process is. Those separate agencies building you an asset from agencies renting you one.
- How much does a cold email agency cost?
- Retainers commonly run from a couple of thousand a month upward, sometimes with a per-meeting component. Infrastructure is usually billed separately or passed through, and it is worth asking whether mailbox and domain costs are included, because a hundred mailboxes is meaningful spend on its own.
- What should I ask a cold email agency before signing?
- Who owns the domains and mailboxes afterwards, sends per mailbox per day, how they verify lists, where their data comes from, how fast opt-outs are processed, and whether you get access to the sending accounts and the reply inboxes.
- What are the red flags?
- Guaranteed meeting counts, refusal to say who owns the domains, sending volumes above roughly twenty per mailbox per day, vagueness about where the list came from, and reporting that leads with open rate.
- Should I hire an agency or build in house?
- An agency makes sense when you want to test outbound before committing, or need it running sooner than you can hire. In house makes sense once outbound is a permanent channel, because the domains and reputation are assets that take weeks to build and you want to own them.
Published 20 September 2026. Updated 20 September 2026. Written by the team that runs the infrastructure; numbers come from the platform's own provisioning and sending, and from the providers' published documentation at the time of writing.