How many domains and inboxes you need for cold email
By Travis Heurtelou · 5 min read · October 10, 2026
The short version
- Start from contacts, not inboxes: how many new people do you want to reach each week?
- Each contact gets two emails. Each inbox sends about a dozen cold emails a day. Each domain holds three inboxes.
- 1,000 new contacts a week needs about 34 inboxes on 12 domains.
- Count the list first. If you only have 3,000 reachable buyers, a big fleet just burns through them faster.
Start from contacts
The question people ask is how many inboxes to buy. The question that decides it is how many new people you want to reach each week, and whether the list has that many. Inboxes are cheap. A list of the right buyers is the hard part.
The numbers we use
| Input | Our number | Why |
|---|---|---|
| Emails per contact | 2 | A first email and one follow-up. More steps mostly add sends to people who already decided. |
| Cold sends per inbox per day | About 12 | Low enough that each inbox looks like a person. Warm-up traffic runs on top of this. |
| Inboxes per domain | 3 | Spreads the risk. One bad domain takes three inboxes with it, not thirty. |
| Sending days per week | 5 | Weekdays only. |
The math
Say you want to reach 1,000 new people a week. Two emails each is 2,000 sends a week, or 400 a day over five days. At about 12 cold sends per inbox, that's 34 inboxes. At three per domain, 12 domains.
| New contacts per week | Sends per day | Inboxes | Domains |
|---|---|---|---|
| 250 | 100 | 9 | 3 |
| 500 | 200 | 17 | 6 |
| 1,000 | 400 | 34 | 12 |
| 2,500 | 1,000 | 84 | 28 |
Add a few spare domains on top. Some will pick up a blacklist entry or a bad week, and you want something already warmed to move to.
Check the list before you buy anything
At 1,000 new contacts a week you use 4,000 a month. If your market has 3,000 reachable buyers with a verified email, you're done in three weeks and the fleet sits idle. Count the buyers first: companies that fit, the right person at each, an email that verifies. Then size the fleet to the list.
For a company selling to a narrow market, that often means a smaller fleet running for longer, with new names added as the signal you're tracking turns them up: a new job post, a new location, a new contract.
What the domains should look like
Plain names that read like a company, on .com where you can get it. Not your brand with a hyphen, and not words like 'leads' or 'outreach'. Point each one at your website so a curious reader lands somewhere real. Set up SPF, DKIM and DMARC on every one before the first warm-up email.
New contacts per week × 2 ÷ 5 days ÷ 12 per inbox = inboxes. Divide by 3 for domains. Then check the list can feed it.
Questions
Can I send more per inbox to save money?
The inboxes burn out sooner. Inboxes are the cheapest part of the system. The list and the domain reputation are the expensive parts to replace.
Google Workspace or Microsoft 365 inboxes?
A mix is fine. What matters more is that they're warmed and that the domains are set up correctly.
Should I send from my main domain at low volume?
No. Even a little cold email on your main domain puts the inbox your customers and invoices use at risk.
Related
Rather we just run it?
We work one market at a time and hand you the introductions worth having. If your market does not fit, we will tell you before you spend a dollar.
Request a GTM Audit