Mailbox calculator
How many mailboxes does your cold email campaign need?
Set the volume and the timeframe. The calculator shows how many mailboxes and domains you need to send it without pushing any single mailbox past a safe daily limit.
Campaign parameters
Define your campaign volume and timeline
Your infrastructure
What you need to send this campaign safely
Primary · actively sending your campaign
Mailboxes
Domains
Backup · keeps sending while a flagged mailbox rests
Mailboxes
Domains
Scaling · warm-up takes time, a ready pool lets you scale instantly
Mailboxes
Domains
Total mailboxes
Total domains
- Keep cold sending to 25–30 emails a day per mailbox; more can trigger spam filters.
- Put 2–3 mailboxes on a domain, so one burned domain takes down as few mailboxes as possible.
- New domains need 2–3 weeks of warm-up before they send campaigns.
- Keep a 20–30% backup pool, so a flagged mailbox can rest while another takes its place.