Email Glossary

Bounce Rate

Email bounce rate is the percentage of emails that are returned as undeliverable. Bounces are classified as 'hard' (permanent failures) or 'soft' (temporary issues). High bounce rates damage sender reputation.

Hard Bounces vs Soft Bounces

Hard Bounces (permanent failures):

  • ●Invalid email address (typo, doesn't exist)
  • ●Domain doesn't exist
  • ●Recipient server blocked you
  • ●Email address deactivated

Hard bounces should be immediately removed from your list. Continuing to send to hard bounces signals you're not managing your list properly.

Soft Bounces (temporary failures):

  • ●Mailbox full
  • ●Server temporarily unavailable
  • ●Message too large
  • ●Auto-reply/out of office

Soft bounces can retry. After 3-5 soft bounces, convert to hard bounce and remove.

Acceptable Bounce Rates

Industry benchmarks:

Total Bounce Rate: Under 2% Hard Bounce Rate: Under 0.5%

Above these thresholds, ISPs may:

  • ●Throttle your sending
  • ●Send more emails to spam
  • ●Temporarily block your IP/domain
  • ●Permanently blacklist you

Some industries (B2B, older lists) naturally have higher bounce rates. Monitor your specific trends rather than just benchmarks.

Reducing Bounce Rates

Prevention:

  • ●Use double opt-in for new signups
  • ●Validate emails at point of collection
  • ●Remove obviously invalid addresses before sending

Maintenance:

  • ●Remove hard bounces immediately
  • ●Monitor soft bounces and remove after repeated failures
  • ●Regularly clean inactive subscribers
  • ●Re-confirm old or dormant lists before sending

Technical:

  • ●Check SPF, DKIM, DMARC configuration
  • ●Ensure sending infrastructure is properly configured
  • ●Monitor blacklists and fix issues quickly

Related Terms

Email Deliverability

The ability of your emails to reach recipients' inboxes instead of spam.

Sender Reputation

A score ISPs assign to your sending IP and domain based on email behavior.

List Hygiene

The practice of maintaining a clean email list by removing invalid and inactive addresses.

Frequently Asked Questions

Why did my bounce rate suddenly spike?
Common causes: importing an old list, sending to purchased lists, email validation service failure, or being blocked by a major ISP. Check your recent sends for patterns, which domain bounced most? Were these new contacts?
How do I handle soft bounces?
Retry soft bounces for up to 72 hours. If they continue bouncing after 3-5 attempts, treat them as hard bounces and remove them. Some soft bounces (like 'mailbox full') may clear up if you wait.
Should I email validation before every send?
Validate new addresses at collection. For existing lists, validate before major campaigns or if you haven't sent in a while. Regular senders with good list hygiene don't need to validate before every send.
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