How many inboxes do you need for cold email?
Start from the meetings you want. This cold email infrastructure calculator gives you the inboxes, domains, first send date and monthly cost, with the math shown.
Sent. Check your inbox in a minute.
How we got this
A planning model, not a deliverability guarantee. Prices vary by country, plan and reseller.
How many inboxes do I need for cold email?
Divide the cold emails you need to send per day by the emails each inbox can safely send per day, round up, then add about 20% spare inboxes. At 25 emails per inbox per day, 300 emails a day needs 12 sending inboxes plus 3 spares, so 15, spread across 8 sending domains at 2 inboxes each.
prospects = meetings ÷ meeting rate ÷ positive share ÷ reply rate
emails per day = prospects × steps ÷ sending days
inboxes = round up (emails per day ÷ emails per inbox) + spares
domains = round up (inboxes ÷ inboxes per domain)
Checked October 2026: Google sending limits, Google sender guidelines, Smartlead pricing. Mailbox prices are placeholders: see Google Workspace and Microsoft 365.
How many cold emails per inbox per day?
Plan for 20 to 30 cold emails per inbox per day, after warmup, and treat that as a ceiling rather than a target. Provider limits are far higher: Google Workspace allows 2,000 messages per user per day. The gap is the point. Cold volume should look like a person, not like the limit.
Per user. 500 on trial accounts.
Google's guidance: stay below 0.1%.
SPF, DKIM, DMARC, one-click unsubscribe.
Base 6,000 sends to Prime 500,000.
Cold email infrastructure setup checklist
Separate sending domains keep cold email risk away from the domain your customers, invoices and hiring emails depend on; see deliverability. And size inboxes per campaign: a hard daily cap shared across many campaigns throttles all of them at once.
- Buy the domains from the calculator, close variants of your brand, never your main domain.
- Create the inboxes with real names and photos, 2 or 3 per sending domain, plus spares.
- Authenticate every domain with SPF, DKIM and DMARC, then check it with the email domain checker.
- Start warmup on day one and keep it running after cold sending starts.
- Verify the list before upload, and ramp cold volume up slowly.
- Give each campaign its own inbox capacity. Watch replies and bounces per domain, and rest any domain that slips.
Questions
Questions people ask before they buy inboxes.
At 25 cold emails per inbox per day you need 40 sending inboxes, plus 8 spares at a 20 percent buffer, so 48 in total. At 2 inboxes per domain that is 24 sending domains. Change the emails per inbox and the answer moves in direct proportion.
Not in this calculator. Emails per inbox per day here means cold campaign emails only. Warmup traffic runs on top, and every message still counts toward your provider's own daily cap. Google Workspace caps each user at 2,000 messages a day, which is far above any sensible cold volume.
Google and Microsoft do not publish a warmup period. The calculator defaults to 3 weeks as a cautious planning assumption, with 2 weeks as a common lower end. Treat it as a minimum and start slowly even after warmup ends.
You can, but a deliverability problem then lands on the domain your invoices, support and hiring emails come from. Google asks every sender to keep the spam rate reported in Postmaster Tools below 0.3 percent. Separate sending domains keep that risk away from your main domain.
Free 30 minute signal audit
Got your inbox count? Now email the right people.
Infrastructure is the easy half. The signal audit finds the buying signals your market gives off, so those inboxes email people with a reason to reply.
Pick a time in the calendar below to schedule a 30 minute call with me.
- 01You talk. Who you sell to and what you send today.
- 02We map. The signals that fire for your ICP and the two to start with.
- 03You keep it. The signal map and a budget range, whether or not you build with us.
Ishan Vats, founder of IV Consulting. We run our own outbound on the same system.
More free GTM tools: Signal library · Email domain checker · GTM glossary · GTM and CRM setup
Loading the calendar. If it does not appear, book the signal audit on cal.com.