Inbox capacity planning

Calculate how many cold email inboxes you need before you provision.

Plan inbox count from the actual send load: list size, touches per prospect, business-day cadence, and risk tolerance.

Calculator

Model the send load.

Inbox count is only one readiness input. GTM also checks DNS, SMTP/IMAP smoke tests, seed placement evidence, and launch gates before export.

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Capacity recommendation

Shared SMTP control plane

Lowest-friction package for readiness-gated SMTP inboxes on managed shared capacity.

Estimated monthly cost

$226

Planning estimate only.

Monthly emails

15,000

5,000 prospects x 3 touches.

Daily send requirement

693

Spread across 5 send days/week.

Recommended inboxes

28

25 emails/inbox/day cap.

Recommended domains

10

3 inboxes/domain by default.

Infrastructure caps

SMTP IP capacity
2
Domain daily cap
100
IP daily cap
3,000
Warmup assumption
30 days

Per-IP utilization should stay below 80 percent before adding traffic. Scale horizontally with more IPs or domains before raising inbox caps.

Cost assumptions

Shared SMTP control plane platform planning baseline$99
28 inboxes$112
10 managed domains$15

Domain registration, taxes, discounts, support tiers, and real Microsoft/Google reseller SKUs can change the final quote.

Readiness notes

  • Treat this as a planning estimate, not a quote or deliverability guarantee.
  • Readiness gates, seed-placement evidence, and fresh SMTP/IMAP smoke tests still decide exportability.
  • GTM-managed shared SMTP capacity; IP count is a planning signal, not a line item.

Common questions

How many emails per day should each cold email inbox send?

Use conservative caps for new infrastructure. This calculator defaults to 25 emails per inbox per day and only models higher caps when you explicitly choose a higher-risk profile.

Does the recommended inbox count mean it is safe to send immediately?

No. The result is a planning estimate. Actual sending should still wait for readiness checks, seed-placement evidence, and launch-gate approval.

Related workflows

SMTP package calculator

Model inboxes, domains, SMTP capacity, and monthly planning cost together.

DNS & auth checker

Check whether domain authentication is ready before inboxes are used.

Inbox readiness checker

Check whether a domain is set up to support the capacity you just planned.

Inboxes per domain guide

The reasoning behind conservative inbox-per-domain assumptions.

Next step

Turn capacity planning into an API-first provisioning and readiness workflow.

Read the agency quickstart