How much can you safely send?
The mailbox capacity calculator for cold email: enter your mailboxes and limits, get your true daily and monthly ceiling — and the replies to expect. No signup.
Your inputs
Fill in your real setup
Total mailboxes actively sending cold email.
20–30 is the safe range for warmed mailboxes.
Used to check your mailboxes-per-domain risk.
Each new prospect consumes one send per step.
Your safe capacity
What your setup can safely send
Assumes warmed mailboxes on domains older than 30 days. New setup? Warm up first.
This tool is for guidance only. Your results may vary.
How the math works
Capacity is mailboxes × per-mailbox daily limit. The safe limit for a warmed mailbox is 20–30 cold sends per day — push past that and placement quietly degrades long before anything looks broken. Full breakdown of daily limits here.
Prospect capacity divides monthly volume by your sequence length — a 5-step sequence means each new prospect consumes five sends. Replies assume the typical 2–5% total reply rate; your list quality decides which end of that range you get.
The number this calculator can't give you: how much of that capacity is actually healthy right now. A mailbox that silently disconnected or a domain drifting toward a blacklist takes real capacity to zero while the plan says otherwise — that gap is what ColdOps watches across every client workspace.