How many inboxes do you actually need?
Do the maths first.
Start with your daily sending target. We’ll turn it into domains, mailboxes and a ramp-up plan using the rules we run for clients.
14 days of warm-up + 6 daily ramp steps from 8 to 20 = about 20 days. The full-volume estimate uses the 20-send mailbox cap.
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Keep this plan
Download your domain count, mailbox count and volume plan together.
Plan capacity before you buy inboxes.
A sending target is useful only when the infrastructure behind it has room to operate. This calculator works from a cap of 40 campaign sends per domain per day, with a maximum of two mailboxes on each domain. Divide your daily target by 40 and round up to find the domain count. Each domain adds two mailboxes, and your actual daily volume is shared across them.
New mailboxes spend 14 days warming up with no campaign sends. After that, the plan starts at eight sends per mailbox and rises by two a day toward the 20-send cap. That is approximately 20 days from the beginning of warm-up to full planned capacity. Warm-up stays on after campaigns start.
The domain estimate uses approximately $13 per domain per year. It is a planning allowance, not a quote. Mailbox pricing is separate, so use the current provider price before committing. Buying more infrastructure should follow a credible market and message, rather than substitute for them.