Free Tool

Cold Email Infrastructure Calculator

Enter your target daily sending volume and get the domains, mailboxes, and warmup timeline you need. Built by REInbox from the same infrastructure we run for real estate wholesalers and investors.

Target daily send volume 200/day
50/day2,000/day
--
Domains needed
--
Total mailboxes
--
Mailboxes per domain
Warmup period: 15–30 days before you're sending your full target volume. Launch campaigns only after warmup is complete.
Warmup stagePer mailbox/dayTotal campaign volume/day

This is exactly the setup we configure for every client, domains, mailboxes, warmup, and monitoring, before a single cold email goes out.

Learn More Here
Assumptions: 25-30 emails per mailbox per day at full warmup, 3 mailboxes per domain, 15-30 days to warm up before launching campaigns. These are conservative starting points, not hard limits. Real client accounts we run range from 12/mailbox/day on newer or higher-risk domains up to 45-50/mailbox/day on established ones. Your actual safe volume depends on domain age, sending history, and how the account has warmed up.

Frequently asked questions

How many mailboxes do I need for cold email?

Divide your target daily send volume by the safe per-mailbox limit, roughly 25-30 emails per mailbox per day once fully warmed up. Sending 200 emails a day takes about 8 mailboxes.

How many domains do I need for cold email?

Spread mailboxes across multiple domains rather than concentrating them on one, roughly 3 mailboxes per domain, so a single deliverability problem doesn't take down your whole sending capacity at once.

How long does email warmup take?

Typically 15 to 30 days. New mailboxes start at 5-10 emails a day and ramp gradually. Sending full volume from day one on a brand new mailbox is the fastest way to get flagged. Give warmup the full window before launching campaigns.

How many cold emails can I send per mailbox per day?

About 25-30 per day once a mailbox is fully warmed up, less on newer or higher-risk domains. Real client accounts we run range from 12 to 50 per mailbox per day depending on domain age and risk tolerance.