Keep hard bounces under 2% of sends. Above that, filters assume a purchased or scraped list. Verify every address before sending, send to catch-all domains at lower volume, and remove anything that bounced once.
Why bounces matter more than you think
A bounce is a receiver telling you the address does not exist. Many bounces in a short window is the signature of a bought list. Mailbox providers treat it as a strong spam signal, independent of your copy or authentication.
Causes
- Unverified lists from data tools. Even good tools are 5% to 15% stale.
- Catch-all domains, which accept everything at SMTP time and bounce later.
- Role addresses (info@, sales@) that are often abandoned.
- Old exports from a CRM.
Getting under 2%
- Verify every list the day you send it, not when you built it.
- Separate catch-all results and send to them at a third of normal volume.
- Suppress every hard bounce across all campaigns and domains.
- If a batch bounces over 5%, stop the campaign and rebuild the list.
Bounces also distort your numbers. Measure reply rate on delivered, not sent, in the ROI calculator.
Turn send volume and reply rates into meetings, deals, revenue and cost per meeting.
Questions
Is a 5% bounce rate bad for cold email?
Yes. It is more than double the safe threshold and will show up in placement within days. Stop and verify the list.
Do soft bounces count?
Occasional soft bounces (full mailbox, temporary error) are normal. Repeated soft bounces to the same address should be treated as hard.