Short answer Emails a day = meetings a month × emails per meeting ÷ working days. Mailboxes = emails a day ÷ cold emails per mailbox, plus about 10% spares. Domains = mailboxes ÷ 2–3. If you don’t know your emails-per-meeting number yet, plan with 150–400 and measure your own in the first 30 days.
Emails a working day76
Mailboxes, with spares5
Sending domains (min. 3)3
Mailbox cost a month$35
New contacts a working day25
Verified market you need2,133
Positive replies a day1.1
Fulfilment time a day0.4 h
How the numbers work
- Emails a working day = meetings a month × emails per meeting ÷ working days. Most B2B sending happens Monday to Friday, about 21 days a month.
- Mailboxes = emails a day ÷ cold emails per mailbox, plus your spare percentage, rounded up. Grow by adding mailboxes and domains, never by pushing more through each one.
- Domains = mailboxes ÷ mailboxes per domain, rounded up, and never fewer than three, so losing one never stops you.
- Verified market = new contacts a day × the working days in your contact cycle. If the market you can actually reach is smaller than this, slow down or widen your segments; don’t email the same people more often.
- Fulfilment = positive replies a day × minutes per reply. Above a few hours a day, templatise what you send or switch to an offer that scales.
These are planning numbers. Your own emails-per-meeting figure, measured over your first 30 days of sending, beats any default. Mailbox cost covers mailboxes only; sending tools, data and verification usually add about as much again.
Behind the numbers
Why these defaults, and what they cost
The playbook explains each setting, the costs people forget, how to size your market from a filter count, and when to stop scaling.
Related: What the software costs for this setup · How many cold emails per mailbox per day · How to warm up a cold email domain · Cold email benchmarks