How many mailboxes does your target need?
Work backwards from meetings. Six steps of arithmetic, with every assumption named so you can substitute your own instead of ours.
- Six-step formula
- Your rates, not ours
- No email required
The short answer
- Work backwards, always: meetings wanted, then positive replies, then total replies, then contacts, then sends, then mailboxes and domains. Working forwards from a volume you can afford produces a plan with no relationship to a target.
- The only rates that matter are yours. If you have sent before, use your own reply and booking rates. If you have not, run a small campaign to find them before planning the big one.
- The output is a constraint, not a permission. Needing eighty mailboxes to hit a number usually means the offer or the list is wrong rather than that you should buy eighty mailboxes.
The formula, not a widget
The six steps
- Meetings wanted per month. Start here and nowhere else. Call it M.
- Positive replies needed = M ÷ your booking rate from a positive reply. Not every interested reply becomes a meeting.
- Total replies needed = positive replies ÷ the share of replies that are positive. Most replies are not interest; they are questions, referrals and polite refusals.
- Contacts needed = total replies ÷ your reply rate per contact across the whole sequence. Per contact, not per email, since one person receives several touches.
- Emails sent = contacts × steps in your sequence, reduced by the share who reply early and stop receiving the rest.
- Mailboxes = emails sent per day ÷ your per-mailbox daily cap. Then domains = mailboxes ÷ how many you are willing to run per domain.
A worked example
Every rate here is an illustration. Replace all four with your own before you buy anything.
| Step | Calculation | Result |
|---|---|---|
| Meetings wanted | The target you were given | 10 per month |
| Positive replies | 10 ÷ 0.5 booking rate from a positive reply | 20 positive replies |
| Total replies | 20 ÷ 0.3 share of replies that are positive | 67 replies |
| Contacts | 67 ÷ 0.03 reply rate per contact | 2,233 contacts |
| Emails sent | 2,233 contacts × about 3.5 effective touches | About 7,800 emails a month |
| Per working day | 7,800 ÷ 21 working days | About 370 a day |
| Mailboxes | 370 ÷ a conservative 30 a day per mailbox | About 12 mailboxes |
| Domains | 12 mailboxes at 3 per domain | 4 domains |
Illustrative rates only. A three percent reply rate is neither a promise nor a benchmark; it is a placeholder to show the shape of the arithmetic.
What to do with the answer
If the number of mailboxes looks large, the correct response is usually not to buy them. Two other levers move the arithmetic much further: a better-targeted list raises the reply rate, and a better offer raises the share of replies that are positive. Both compound backwards through every step above.
Volume is the lever with the worst return and the highest risk. More mailboxes means more domains, more warmup, more reputation surface and more ways to fail quietly.
The constraints the formula assumes
- Every mailbox is warmed before it sends. SalesCrew does not warm mailboxes; that is another tool's job.
- Daily caps are enforced rather than intended. SalesCrew applies per-account and per-domain caps with cooldown stamps.
- Suppression is applied when the audience is frozen and re-checked at send, so your contact count is the real one.
- A reply pauses the sequence for that contact, which is why step five reduces the touch count.
- At least three days between touches per contact, which sets how long a sequence takes to run.
Find your own rates before you scale anyone else's
A small campaign that measures four numbers is worth more than a plan built on averages.