Free tool
Cold Email Volume Calculator
How many mailboxes, how many domains, and how long before you can actually send at that volume.
How many mailboxes do you need
Target
Sending limits
30 to 50 is the usual safe band. Lower it for a brand new domain.
Two or three keeps one bad mailbox from taking the domain with it.
Pre-warmed mailboxes shorten this. New domains should not.
Costs
Your list
Steps in the sequence, including the first email.
Warmup ramp
A new mailbox that opens at full volume gets filtered. This is the schedule to reach your target, and the earliest week you can actually send it.
| Week | Per mailbox | Total per day | Share of target |
|---|---|---|---|
| Week 1 | 11 | 357 | 36% |
| Week 2 | 18 | 612 | 61% |
| Week 3 | 26 | 867 | 87% |
| Week 4 onwards | 30 | 1,020 | 100% |
Working through your list
The arithmetic
- Mailboxes
- ceil(1000 ÷ 30) = 34
- Domains
- ceil(34 ÷ 3) = 12
- Monthly capacity
- 1000 × 5 × 4.33 = 21,650
- First month cost
- (34 × $3) + (12 × $12) = $246
Volume is an infrastructure problem
Everyone starts with a number of emails they want out the door each day and then discovers that number is not a setting, it is a build. Mailbox providers cap what one address can send before it looks automated, so daily volume is really a question of how many mailboxes you are prepared to run, across how many domains, and how many weeks of warmup you can wait through first.
Why 30 to 50 a day and not 500
The limit is behavioural, not technical. A mailbox that sends five hundred near-identical messages a day to people who never wrote first does not look like a person, and filtering reacts to that pattern rather than to your content. Thirty to fifty is where most operators settle. New domains should start lower, around ten to fifteen, and climb.
Never your main domain, and rarely one domain
Cold outreach belongs on separate sending domains, because reputation damage is permanent and you cannot afford it on the domain your invoices go out from. Spreading mailboxes two or three to a domain also contains the blast radius: one flagged mailbox costs you a third of a domain rather than all of your capacity.
Warmup is the part people cut and regret
A new mailbox needs a couple of weeks of gradually rising volume before it can carry its full load. Skipping it is the single most common reason a technically perfect setup lands in spam from day one. Plan the ramp into your timeline, or buy pre-warmed mailboxes and start at a lower ceiling anyway.
Frequently asked questions
Sizing a cold email setup
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