What Is Email Bounce Rate?
Email bounce rate is the percentage of emails in a send that were rejected by the recipient's mail server and returned to the sender. It's one of the most important deliverability metrics you can track.
Formula: (Bounced emails ÷ Total emails sent) × 100
Hard Bounce vs Soft Bounce
Not all bounces are equal.
Hard Bounces
A hard bounce is a permanent delivery failure. The address doesn't exist, the domain is gone, or the mail server has explicitly blocked you. These addresses will never receive email.
Examples:
user@nonexistentdomain.com— domain doesn't existdeleted.user@gmail.com— account was closedtypo@gmial.com— syntax was valid but domain doesn't handle mail
Action: Remove hard bounces from your list immediately and permanently.
Soft Bounces
A soft bounce is a temporary failure. The address exists but couldn't receive your email right now.
Examples:
- Mailbox full
- Server temporarily unavailable
- Message too large
Action: Retry soft bounces a few times. If they keep bouncing, remove them too.
What's a Good Bounce Rate?
Industry benchmarks:
| Rate | Status |
|---|---|
| < 2% | Healthy |
| 2–5% | Warning zone — investigate |
| > 5% | Dangerous — your reputation is at risk |
Gmail, Outlook, and Yahoo all monitor senders' bounce rates. Cross their thresholds and your emails start landing in spam — or stop being delivered entirely.
Why Bounce Rate Spikes
- Old list — Email addresses decay at ~30% per year. A list from 18 months ago is already stale.
- No double opt-in — Users mistype their address at signup and you never catch it.
- Purchased lists — These are almost always full of invalid, recycled, or spam-trap addresses.
- Role addresses —
info@,admin@,noreply@addresses churn frequently.
How to Fix a High Bounce Rate
Step 1: Verify Your List Before Sending
Use The Mailtrix to run your list through a full SMTP verification before every campaign. Upload your CSV, start the job, download only the valid addresses.
A single cleaning pass before a major send can drop your bounce rate from 8% to under 1%.
Step 2: Verify at Signup
Integrate the Mailtrix API into your signup flow to catch invalid addresses in real time — before they ever enter your list.
Step 3: Re-verify Old Segments
Any segment you haven't emailed in 3+ months should be re-verified. Addresses that were valid when you collected them may not be valid today.
Step 4: Remove Unengaged Contacts
Even valid addresses that never open your emails are a signal problem. Inbox providers use engagement signals — not just bounce rates — to judge your reputation.
The fastest way to fix a bounce rate problem is to verify your list. Start free on The Mailtrix — 100 free credits, no card required.