Tool

Email bounce rate calculator

See what a bounce rate does to a sending domain, not just to one campaign.

This tool only reads public DNS or runs in your browser. It does not spend verification credits.

Emails sentBounced

4.00%

2–5% is already enough to hurt warmup. Verify the rest of the file before you scale volume.

What this calculator is for

Bounce rate is bounced messages divided by messages sent, over a window you choose. The number is easy. The cost is not the bounced send. It is what happens to the sending domain afterwards.

Plug in a list size and a bounce rate. The point of the model is to make "we'll just send it" expensive enough to see on a screen before you spend reputation.

This runs in your browser. No credits.

Hard vs soft

Hard bounces — mailbox does not exist, domain does not accept mail — are the ones guessed lists produce. They count the most.

Soft bounces — full mailbox, temporary outage — should be retried with a light touch, not immediately treated as "bad data."

If a vendor reports a single "bounce rate" without the split, ask. A 4% soft-bounce week during an Azure outage is not the same as 4% user unknown.

Thresholds, honestly

Mailbox providers do not publish a single magic cut-off. Practitioners talk about roughly 2–5% as the range where domains start to be treated as suspect. We are not going to invent a more precise number than the providers themselves print. Stay under 2% on purpose. Treat 5% as a fire.

A new or warming domain has less room than a domain with years of clean history.

Why verification is the cheap side of the trade

Checking a mailbox before send costs a fraction of a cent when it hits, and nothing when it misses, on our pricing. Recovering a domain that landed in spam costs weeks of throttling across every campaign using that domain — sales mail, password resets, the lot, if you made the mistake of sending marketing from the corporate apex.

The calculator is there to make that mismatch visible. The verifier is there to not need the calculator.

How to use the number in a team conversation

"We bought 10,000 rows at 2 cents" is incomplete. If 3,000 will hard-bounce, you did not buy 10,000 conversations. You bought a reputation event. Recast the purchase as: cost of data + cost of credits to verify + expected remaining sendable rows. If the leftover verified set is 4,000, that is your real list size.