Bounce rate is the single most important metric for email sender reputation.
Understanding Bounce Types
Hard Bounces
Permanent delivery failures — the address doesn't exist. Remove immediately. Never retry.
Soft Bounces
Temporary failures — mailbox full, server unavailable, rate-limited. Retry 1-3 times over 72 hours.
The 2% Rule
Major inbox providers track your bounce rate. Exceeding 2% triggers:
- Spam folder placement
- Throttling — sending speed reduced
- Blocklisting — domain added to blocklists
- Permanent ban
Step-by-Step Plan
Step 1: Verify Before You Send
Use EmailZeno bulk verification to catch:
- Invalid addresses (syntax and SMTP)
- Disposable/temporary addresses
- Role-based accounts
- Catch-all domains
Step 2: Segment by Risk
| Category | Action |
|---|---|
| Verified deliverable | Send normally |
| Risk (accept-all) | Reduce frequency |
| Undeliverable | Remove |
| Unknown | Re-verify |
Step 3: Monitor Re-engagement
After 90 days of inactivity, move contacts to re-engagement flow. Remove after 3 attempts.
Step 4: Sunset Rules
Remove addresses inactive for 6+ months. Stale addresses rot — people change jobs, abandon inboxes.
How EmailZeno Helps
- Real-time API verification at signup
- Bulk verification for campaigns
- Honest SMTP transcripts
- Webhook notifications
Conclusion
Verify before every send, segment by confidence, sunset stale contacts, and always stay under 2%.
