# How Many Mailboxes and Domains Do You Need for Cold Email?

URL: https://warmerly.com/blog/how-many-mailboxes-and-domains-for-cold-email
Published: 2026-10-14
Reading time: 5 minutes
Tags: Setup, Cold email, Infrastructure

> Work out how many mailboxes and domains you need for a daily cold email target, with a simple formula, worked examples and the limits that keep it safe.

Divide your daily send target by 40, which is a cautious ceiling for one warmed mailbox, and round up. That is your mailbox count. Then put two to three mailboxes on each domain, so divide the mailbox count by three and round up for your domains. A target of 200 emails a day needs 5 mailboxes and 2 domains.

> **How this was checked**: The numbers are the guideline already published on our sending limits page: about 40 to 50 a day for a warmed mailbox, 5 to 10 for a brand-new one, and two to three mailboxes per domain. They are cautious starting points, not guarantees, and providers' own limits are far higher. No statistics are used.

## The formula

1. Mailboxes = daily target divided by 40, rounded up. Use 50 only for mailboxes that have sent steadily for a long time.
2. Domains = mailboxes divided by 3, rounded up. Use 2 per domain if you want more margin.
3. Add one spare mailbox per five, so a paused or unhealthy mailbox does not stop the campaign.

**Worked examples at 40 emails per warmed mailbox and three mailboxes per domain**
| Daily target | Mailboxes | Domains | With a spare |
| --- | --- | --- | --- |
| 50 | 2 | 1 | 3 mailboxes |
| 100 | 3 | 1 | 4 mailboxes, 2 domains |
| 200 | 5 | 2 | 6 mailboxes |
| 400 | 10 | 4 | 12 mailboxes |

## The target is not day-one volume

These totals are where you arrive, not where you start. A new mailbox sends 5 to 10 a day at first. Warmerly's campaign ramp opens at 3 per mailbox on day one and adds one per sending day up to a default ceiling of 15, so a new set of mailboxes takes weeks to reach a full target. Plan for that when you set a date for the volume you want.

## Why not just send more from fewer mailboxes?

- Filters judge each mailbox and each domain. A spike on one mailbox is easy to see.
- Domain totals compound. Three mailboxes sending 60 each look like 180 a day from one domain.
- A problem on one domain stays on that domain. Spreading across domains limits the damage.

## Keep the sums honest

More mailboxes do not fix a poor list or weak targeting. If bounces or complaints are rising, add nothing: pause, clean the list and check authentication. Extra volume of the wrong mail from more domains is how a whole set-up gets listed.

**Next steps**
- [Cold email sending limits by provider](https://warmerly.com/email-outreach/limits)
- [Free warmup calculator](https://warmerly.com/warmup-calculator)
- [Cold email launch checklist](https://warmerly.com/blog/cold-email-launch-checklist-founder-sdr-agency)

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