Guide

How to tell if a business email list is accurate (bounce rates explained)

By Andrew Ornelas ·

Every list seller says their emails are "verified." That word can mean very different things. Here's how to judge a business email list yourself, and what the numbers actually mean.

What a bounce is

A bounce is an email that couldn't be delivered. There are two kinds:

  • Hard bounce — a permanent failure. The address or domain doesn't exist. These hurt your sender reputation and should be removed right away.
  • Soft bounce — a temporary problem, like a full mailbox or a server that's briefly down. These often deliver on a later try.

Spam-filter blocks and out-of-office replies are different again. When you judge a list, focus on hard bounces.

Bounce rate, in plain numbers

Bounce rate is bounced emails divided by emails sent. Send 500, have 20 hard-bounce, and your hard-bounce rate is 4%. "Deliverability" in this sense is the flip side: about 96% of those emails were accepted.

Opt-in newsletter lists usually bounce very little. Cold B2B lists of local businesses bounce more, because small businesses change staff, domains and email providers often. As a rough guide for cold local B2B email:

  • Low single digits — a well-built, recently checked list.
  • Around 5–10% — usable, but clean it before sending more.
  • Over 10% — a red flag. Stop and clean the list before you damage your sending domain.

Email providers watch bounces and spam complaints closely. High numbers can push your future emails into spam, even the good ones.

What "verified" can mean

  • Syntax check — the address is formatted correctly. This is the bare minimum.
  • MX check — the domain has mail servers that can receive email. This catches dead domains and typos, a big share of bounces.
  • Mailbox check — testing whether the specific address exists. Useful, but some servers won't say.
  • Catch-all domains — some businesses accept mail for any address at their domain, so a check can't confirm a mailbox. Treat these as "probably fine," not certain.

Also look at which emails are in the list. Generic no-reply and support inboxes rarely reach a decision-maker. An owner's address taken from the business's own website is usually better than a guessed pattern.

How to test a list before a big send

  1. Look at a sample. Do the businesses exist and match your area? Do the domains match the business websites?
  2. Send a small first batch — say 50 to 100 — from a warmed-up sending address.
  3. Measure hard bounces from that batch before sending the rest.
  4. Remove every hard bounce right away, and honor every opt-out.
  5. Re-check older lists. Business email data goes stale; a list that was clean a year ago may not be now.

Questions to ask a list seller

  • When was the data gathered and checked?
  • What checks were run — syntax, MX, mailbox?
  • Are generic inboxes removed?
  • What happens if a lot of emails bounce?

Be wary of anyone promising 100% accuracy. Business information changes every day.

How Prospect Miner handles it

Prospect Miner pulls lists fresh when you order and checks emails before delivery, removing dead domains and no-reply inboxes. Our target is fewer than 10% hard bounces; if more than 10% of a list's emails hard-bounce and you tell us within 14 days, we replace the bounced emails above that line. See our terms and pricing, or read how to build a lead list by zip code or radius.

Want a list built for your area? Request a lead list — tell us the zip code, city or radius and the industries, and we'll reply with a quote.

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