Free tools for preparing, validating, and scaling outbound email safely.
Estimate mailboxes and domains for your send plan.
Plan mailbox and domain counts from daily or monthly volume — or from a meetings goal. Planning estimate only — not a provider or deliverability guarantee.
Empty
Choose a mode, enter your target volume or meetings, and calculate a planning estimate.
Why this matters
Capacity planning is part of safer outbound.
Planning, not a guarantee
This calculator turns volume or meeting goals into mailbox and domain counts using editable assumptions — not provider limits or deliverability outcomes.
Three input modes
Start from monthly sends, daily sends, or a target number of meetings per month. The tool derives the other volumes from your assumptions.
Tune the assumptions
Safe sends per mailbox, reply rate, meeting rate, and cost inputs reflect how your team actually operates. Adjust them to match your stack.
Related: Spam Content Checker · SPF Checker
Straight answers
Mailbox Calculator FAQ
Is this a deliverability recommendation?+−
No. It is a planning estimate for capacity and cost — not a guarantee that any volume is safe for your domain or provider.
Why cap sends per mailbox?+−
Most outbound programs limit daily volume per inbox to protect reputation. The default assumes a conservative per-mailbox cap you can change.
Can I work backward from meetings?+−
Yes. Meetings mode uses reply and meeting rates to estimate the send volume needed to hit your monthly meeting target.
Next step
Plan drafted. Ready to run outreach you approve first.
OmniReach drafts personalized LinkedIn and email sequences. You review the first touch — nothing sends without a deliberate launch.