How many inboxes and domains do you need for cold email?
Set your send target and adjust the assumptions to match your setup. You get inboxes, sending domains, a week-by-week warmup ramp, and the row most guides skip: how many deliverable contacts the target actually requires. Every number traces to an input you can see and change.
Your inputs
Results
How these numbers are calculated
- Contacts required = sends ÷ (1 − bounce rate): 5,000 ÷ 0.85 = 5,883. The bounce rate is your input; verified lists run low single digits, raw scrapes 15% or worse.
- Inboxes = the smallest count whose ramped capacity over 8 weeks covers those contacts, at 5 sending days/week (convention).
- Ramp: starts at 10/inbox/day and grows ~30%/week until your 30/day target. Heuristic, not a standard; the 20-100 range is practitioner lore (Mailreach, Topo guides).
- Sending domains = inboxes ÷ 2 per domain (convention is 2-3).
- The only hard ceilings shown are published: Google Workspace 2,000 messages/account/day and Google's Postmaster spam-rate threshold (under 0.1%, never 0.3%).
| Week | Per inbox / day | All inboxes / week |
|---|---|---|
| 1 | 10 | 350 |
| 2 | 13 | 455 |
| 3 | 17 | 595 |
| 4 | 22 | 770 |
| 5 | 29 | 1,015 |
| 6 | 30 | 1,050 |
| 7 | 30 | 1,050 |
| 8 | 30 | 1,050 |
The right list shrinks this bill.
Nose for Leads finds local businesses that fit your targeting, verifies every email, and only charges when a lead passes.
Why a calculator instead of a number
Ask how many cold emails you can send per day and you get folk numbers that contradict each other: 20 to 50 a day from one guide, around 100 from another, 100 to 200 from a Reddit thread. None of them are standards, so this page does the arithmetic in the open instead. Two numbers here are facts, and they render with their sources: Google Workspace's 2,000 messages per account per day limit and Google's bulk-sender spam-rate threshold (keep it under 0.1%, never at 0.3%). Everything else is practitioner convention, labeled as such and adjustable:
- Sends per inbox per day: 20 to 100 warmed (guides like Mailreach and Topo).
- Inboxes per sending domain: 2 to 3 (convention).
- Warmup ramp: roughly 30% more volume per week until the target (heuristic).
- Sending days: 5 per week (convention).
The bounce-rate input is the one worth arguing about. A verified list runs at low single digits; raw scrapes routinely run 15% or worse, and the posts on why cold email lists bounce and cleaning a scraped list cover why. Move it and watch the infrastructure bill move with it. That gap is our whole product: every lead is mailbox-checked before it counts. When you copy the results, the assumptions copy with them, so the numbers can't drift into folklore when they land in a client doc.
FAQ
How many inboxes do I need for cold email?
It depends on your send target, window, and per-inbox volume, which is why the answer is a calculator and not a number. Enter your target above; the result shows the inbox count, domain count, and week-by-week ramp behind it, with every assumption visible.
How many cold emails per day per inbox?
There is no published standard. Practitioner guides commonly land between 20 and 100 per warmed inbox per day; the only hard ceiling is Google Workspace's published 2,000 messages/day per account. The calculator defaults to 30 and lets you set your own number.
How many sending domains should I split across?
The common convention is 2 to 3 inboxes per sending domain, so domains scale with your inbox count. Splitting protects your main company domain: warmup problems stay on the sending domains. The calculator computes the domain count from your inboxes-per-domain setting.
Do sending limits apply per inbox or per domain?
Google's published limit is per account, meaning per inbox. Reputation, though, accrues to the sending domain as well as the mailbox, which is why practitioners cap volume per inbox and spread inboxes across domains rather than stacking one domain full of accounts.
What bounce rate is safe for cold email?
Google's published threshold is about spam complaints: keep the Postmaster spam rate below 0.1% and never at 0.3%. Bounce rate has no equivalent published ceiling, but high bounces are the classic path to blocks; our post on why purchased leads bounce walks the mechanics. Verifying addresses before sending is how lists reach low single digits.
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