Free tool
Cold email infrastructure calculator
Tell us how many people you want to reach. We'll work out the daily volume, how many inboxes and domains that takes, what it costs each month, and how long it takes to ramp up. Every number shows its math.
People who get email 1 of your sequence.
First email + follow-ups. 3–4 is typical.
5 = weekdays only.
20–50 is the safe range. 30 is a solid default.
2–3 keeps one bad domain from sinking many inboxes.
Google Workspace Business Starter: $7 annual, $8.40 flexible.
A .com is usually $10–15 a year.
Emails / day
416
9,000 / month
Inboxes
14
Domains
5
3 inboxes each
Monthly cost
$103
$11.44 per 1,000 emails
The math
- Sending days / month
- 5 × 52 ÷ 12 = 21.67
- Emails / month
- 3,000 × 3 steps = 9,000
- Emails / day
- ⌈9,000 ÷ 21.67⌉ = 416
- Inboxes
- ⌈416 ÷ 30⌉ = 14
- Domains
- ⌈14 ÷ 3⌉ = 5
- Inbox cost
- 14 × $7.00 = $98.00 / mo
- Domain cost
- 5 × $12.00 ÷ 12 = $5.00 / mo
- Total
- $103.00 / mo · $1,236 first year
Assumes every prospect receives every step. Replies, bounces and unsubscribes stop a sequence early, so real volume runs a little lower. Excludes your sending platform and data costs.
Ramp-up plan
Budget 2–4 weeks of warmup on new inboxes before any cold sends. Then start low and step up weekly, and only add volume while bounces stay under 2% and replies hold.
| Sending week | Per inbox / day | Total / day |
|---|---|---|
| Week 1 | 10 | 140 / 416 |
| Week 2 | 20 | 280 / 416 |
| Week 3 | 30 | 416 |
Sending domain ideas
Enter your main domain and get lookalike domains to send cold email from, so your primary domain's reputation is never on the line.
How the calculator works
Cold email capacity is set by how much each mailbox can send without hurting its reputation, not by how much it's technically allowed to send. So the calculation runs backwards from your goal:
- Monthly emails = new prospects × steps in your sequence. Each prospect gets every follow-up unless they reply, so this is the upper bound.
- Daily volume = monthly emails ÷ sending days. A 5-day week averages 21.7 sending days a month (5 × 52 ÷ 12).
- Inboxes = daily volume ÷ cold emails per inbox, rounded up, plus any spare inboxes you keep on the bench.
- Domains = inboxes ÷ inboxes per domain, rounded up.
- Cost = inboxes × monthly seat price + domains × yearly price ÷ 12.
Choosing the inputs
Emails per inbox: 20–50
Start at 30. Go toward 20 for new domains, strict markets or low reply rates. Go toward 50 only for aged inboxes with clean lists and steady replies. Past 50 you buy volume with reputation, and the bill arrives as spam-folder placement.
Inboxes per domain: 2–3
Mailbox providers score the domain as well as the address. More domains with fewer inboxes each means one blocklisting or reputation dip only takes out a slice of your capacity.
Steps per sequence: 3–4
Every follow-up multiplies your volume. Most replies come from the first two or three emails. A fifth step doubles nothing but your complaint risk.
Spare inboxes: 20–30%
New inboxes need 2–4 weeks before they can carry a full load, and you'll want to rest any inbox whose numbers dip. A warmed bench means you swap one in the same day instead of losing a month of capacity.
Setting up the domains
Once you've picked names from the generator above, each sending domain needs the same setup before a single cold email goes out:
- SPF, DKIM and DMARC on every domain. Google and Yahoo require them, and they're the first thing a filter checks. Verify each one with our SPF, DKIM & DMARC checker, and follow the setup guide if anything fails.
- A 301 redirect to your main site, so a prospect who types the domain in finds you instead of a parked page.
- Real sender names and profile photos on each inbox. Generic names like "sales" read as automation.
- Warmup and a slow ramp, then watch bounces and replies per inbox. The deliverability checklist covers the full pre-send routine, and deliverability fundamentals explains why these limits exist.
Frequently asked questions
- How many inboxes do I need for cold email?
- Divide the emails you send per day (first touches plus follow-ups) by 30. Contacting 3,000 new prospects a month with a 3-step sequence on weekdays is about 416 emails a day, so 14 inboxes. Add 20–30% spare if you want warmed inboxes ready to swap in.
- How many cold emails can one inbox send per day?
- Keep each inbox between 20 and 50 cold emails a day; 30 is a safe default. Gmail's technical limit is far higher, but reputation is judged on engagement and complaints, and those degrade quickly when one mailbox sends hundreds of near-identical messages.
- How many inboxes should I put on one domain?
- Two or three. Reputation is tracked per domain as well as per mailbox, so if a domain gets flagged every inbox on it suffers. Spreading volume over more domains caps the damage from any single one.
- Should I send cold email from my main domain?
- No. Buy separate lookalike domains, redirect them to your main site, and send from those. If a sending domain's reputation drops you replace it; if your primary domain's reputation drops, your invoices, password resets and team email start landing in spam too.
- How long before new inboxes can send at full volume?
- Plan on 2–4 weeks of warmup before the first cold email, then ramp from about 10 cold emails per inbox per day, adding roughly 10 a week while bounce rates and replies stay healthy. Buy domains a month before you need the capacity.
- How much does cold email infrastructure cost?
- Mostly the mailboxes. Google Workspace Business Starter is $7 per user per month on an annual plan ($8.40 flexible), and a .com is about $10–15 a year. At 14 inboxes and 5 domains that is roughly $103 a month before your sending platform and data.
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