Cold email infrastructure costs the sum of four things: domains, mailboxes, sending software, and leads. Domains and mailboxes are the small part, and the cost that decides your result is cost per positive reply, which depends mostly on list cost and reply rate. This article gives the formulas and a worked example. Every price in the example is an assumption you should replace with your own quotes, and we say which is which.
No honest article can give you one number for this, because the inputs are yours: how many emails you send, how many mailboxes you run, where you buy them, and how well the offer lands. So this is a model, not a price list. For what the parts are, read cold email infrastructure: domains, mailboxes and DNS first.
The model
Define the inputs:
| Symbol | Meaning |
|---|---|
| V | Emails sent per sending day, all steps of all sequences |
| c | Per-mailbox daily cap you set |
| k | Mailboxes per sending domain |
| d | Sending days per month |
| s | Emails sent per lead over a whole sequence, on average |
| p_m | Price per mailbox per month |
| p_d | Price per domain per year |
| S | Software or platform cost per month |
| p_l | Price per verified lead |
| r | Positive reply rate per lead contacted |
Then:
Mailboxes needed M = ceil(V / c)
Domains needed D = ceil(M / k)
New leads per month L = (V / s) * d
Monthly cost C = M*p_m + D*p_d/12 + S + L*p_l
Cost per 1,000 emails C / (V*d) * 1000
Positive replies R = L * r
Cost per positive reply C / R
The model leaves things out on purpose: your own time, copywriting, any CRM, the cost of a domain that is burned and must be replaced, and enrichment beyond the lead price. Add them as extra lines if they apply to you.
What public price pages say
We read these on 2026-10-05. They are shown as examples of where a price comes from and not as recommendations. Prices change, vary by region and often depend on annual or monthly billing, so look up the current figure for your case.
| Item | What the public page said | Page |
|---|---|---|
| Google Workspace mailbox | The page displayed euros for our location: Business Starter at 6.80 EUR per user per month at the regular price, with a promotional price for new customers and a discount for annual billing. The page is regional, so your price and currency may differ | Google Workspace pricing |
| Amazon SES transport | $0.10 per 1,000 emails on à-la-carte pricing, $0.12 per GB of attachment data, and $24.95 per month per dedicated IP. The page also lists monthly plans, and says new accounts without recent activity start on a plan | AWS SES pricing |
| Domain registration | Cloudflare Registrar says it does not mark up domain prices, you pay what registries and ICANN charge. The page shows no .com price, so we give none | Cloudflare Registrar |
We did not manage to read a Microsoft 365 price page in a form we could verify, so no Microsoft price is quoted. Provider sending limits are on separate pages, and our infrastructure guide covers them.
Worked example, with assumed numbers
Everything in the next table is an assumption for illustration, not a quote. The goal is to see how the cost splits.
| Input | Assumed value | Why |
|---|---|---|
| V | 300 emails per day | A small program |
| c | 30 emails per mailbox per day | Your own cap, not a provider number |
| k | 3 mailboxes per domain | Your own risk choice |
| d | 22 sending days per month | Weekdays |
| s | 2.5 emails per lead | A three-step sequence where some leads reply or opt out early |
| p_m | $7 per mailbox per month | Placeholder in the range of a business mailbox seat |
| p_d | $12 per domain per year | Placeholder |
| S | $100 per month | Placeholder for sending software |
| p_l | $0.05 per verified lead | Placeholder, varies a lot by source |
| r | 1.5% positive replies per lead | An assumption, not a benchmark |
Step by step:
M = ceil(300 / 30) = 10 mailboxes
D = ceil(10 / 3) = 4 domains
L = (300 / 2.5) * 22 = 2,640 new leads per month
Mailboxes 10 * $7 = $70.00
Domains 4 * $12 / 12 = $4.00
Software = $100.00
Leads 2,640 * $0.05 = $132.00
Total C = $306.00 per month
Emails sent per month 300 * 22 = 6,600
Cost per 1,000 emails 306 / 6.6 = $46.36
Positive replies 2,640*0.015 = 39.6
Cost per positive reply 306 / 39.6 = $7.73
Read the shape, not the figures. Mailboxes and domains are $74 of $306. Leads and software are the larger parts. For comparison, if the 6,600 emails went through Amazon SES at its listed $0.10 per 1,000, the transport line would be $0.66 a month. The per-email price is not what you are paying for.
Sensitivity: what actually moves the cost
Change one input at a time and recompute.
| Change | New monthly cost | New cost per positive reply |
|---|---|---|
| Baseline | $306.00 | $7.73 |
| Per-mailbox cap 20 instead of 30 (15 mailboxes, 5 domains) | $342.00 | $8.64 |
| Per-mailbox cap 40 instead of 30 (8 mailboxes, 3 domains) | $291.00 | $7.35 |
| Positive reply rate 0.75% instead of 1.5% | $306.00 | $15.45 |
| Lead price $0.10 instead of $0.05 | $438.00 | $11.06 |
Two lessons:
- Being cautious with the cap is cheap. Lowering the cap from 30 to 20 adds $36 a month in this example, about 12%. Raising the cap from 30 to 40 saves $15 a month, about 5%, and puts more sending on each mailbox. The saving is small next to what a damaged mailbox costs.
- The reply rate dominates. Halving it doubles the cost per positive reply, and no change in infrastructure price does that. The levers are the list, the offer and the message. See A/B testing for cold email to learn how to find what works.
The hidden cost: a burned domain
The model has no line for a domain that stops delivering, because it is a risk and not a price. Include it as a scenario: if one domain in four needs replacing and replacement means a new domain, new mailboxes and a slower restart, what does the month cost? The worst cases come from list quality and complaints, which Google and Yahoo measure against thresholds of 0.3% (see Gmail and Yahoo bulk sender requirements). Money spent on verifying a list is money spent against this scenario.
Another cost is idle capacity. Mailboxes you pay for and cap low cost the same as mailboxes you use, so size to the volume you will actually send, and add mailboxes when the volume appears.
A spreadsheet version
Put the inputs in cells and copy the formulas:
B1 V B2 c B3 k B4 d B5 s
B6 p_m B7 p_d B8 S B9 p_l B10 r
B12 =CEILING(B1/B2,1) mailboxes
B13 =CEILING(B12/B3,1) domains
B14 =B1/B5*B4 new leads per month
B15 =B12*B6+B13*B7/12+B8+B14*B9 monthly cost
B16 =B15/(B1*B4)*1000 cost per 1,000 emails
B17 =B15/(B14*B10) cost per positive reply
How Dooxout handles this
Dooxout prices as one platform plan plus add-ons, where each add-on (domains, mailboxes, leads, agent tokens) is billed by exactly one unit and can be capped by a budget, so you can add up a bill like the one above before you start. Exact amounts are shared in the demo, so none are given here. See pricing.
The built-in SDR agent can work out how many domains and mailboxes a target volume needs under the current caps, suggest names and estimate the cost from the registrar quote, and it only recommends: a person makes the purchase, at every autonomy level. You can also connect your own mailboxes. Caps per mailbox, domain and channel are set by the server, and the platform warns and recommends while the decision stays with you. More at cold email infrastructure and integrations.
Frequently asked questions
How much does cold email infrastructure cost per month?
It depends on four inputs you choose: daily volume, the per-mailbox cap, mailboxes per domain, and the unit prices you pay. The worked example in this article, with assumed prices, comes to about $306 a month for 300 emails a day. The structure of the cost matters more than that total: mailboxes and domains are a small part, and leads, software and your reply rate decide the cost per result.
What is the cheapest way to send cold email?
Sending the fewest messages that reach the right people. Infrastructure is a small share of the model, so cutting domains or mailboxes saves little, while a list that bounces or complains can cost you the domain. Per-email transport can be very cheap: Amazon SES lists $0.10 per 1,000 emails on its à-la-carte pricing page. Check the provider's terms for cold use before you rely on it.
Do I need a dedicated IP?
Not necessarily. A dedicated IP is a separate cost and a separate reputation to build. Amazon SES lists $24.95 per month per dedicated IP on its pricing page as an example of the extra cost. Mailboxes at Google Workspace or Microsoft 365 send from the provider's own infrastructure, so there is no IP to buy.
What costs more as I scale: mailboxes or leads?
In the worked example, leads. Mailbox and domain costs grow with volume divided by your per-mailbox cap, while the lead cost grows with every new contact. Model your own prices before you decide where to save. See cold email infrastructure for how to size mailboxes.
Sources
The external facts in this article were checked against these pages on . Provider limits and rules change, so check the current page before you rely on a number.