Free Bounce Analyzer
Analyze bounce messages, parse DSN codes (RFC 3463), classify hard vs soft bounces, and get ESP-specific recommendations to improve your email deliverability.
Bounce Analyzer
Analyze bounce messages and DSN codes to classify bounces and get actionable recommendations
Understanding Email Bounces
Hard Bounces (5.x.x)
Permanent delivery failures. DSN codes starting with "5" indicate the email address is invalid, doesn't exist, or has been permanently disabled. These addresses should be removed immediately from your list.
- 5.1.1: User unknown - address doesn't exist
- 5.1.2: Domain not found
- 5.2.1: Mailbox disabled
- 5.7.1: Message rejected/blocked
Soft Bounces (4.x.x)
Temporary delivery failures. DSN codes starting with "4" indicate a temporary issue that might resolve itself. Retry delivery, but suppress if bounces persist for 5-7 days.
- 4.2.2: Mailbox full
- 4.3.1: Mail system full
- 4.4.1: Connection timeout
- 4.4.5: Network congestion
VERP (Variable Envelope Return Path)
VERP is a bounce tracking technique that encodes recipient information in the return-path address (e.g., bounce+user123@domain.com). This allows automated bounce processing and accurate bounce attribution.
- Accurate bounce tracking per recipient
- Automated suppression list updates
- Better list hygiene automation
- ESP-specific VERP formats
Bounce Rate Benchmarks
| Bounce Rate | Status | Action Required |
|---|---|---|
| < 2% | Excellent | Continue current practices |
| 2% - 5% | Good | Monitor trends, improve list hygiene |
| 5% - 10% | Warning | Immediate list cleaning required |
| > 10% | Critical | Stop sending, audit list source, deep clean |
ESP-Specific Bounce Handling
Different ESPs have different bounce handling mechanisms. Select your ESP in the analyzer to get specific instructions for:
- SendGrid: Event Webhooks, Bounce API, automatic suppression lists
- Mailgun: Webhooks, Suppressions API, bounce logs
- Postmark: Bounce Webhook, Bounce API, automatic suppression
- Amazon SES: SNS notifications, bounce handling, complaint feedback
- Gmail/Google Workspace: Postmaster Tools, feedback loop integration
Best Practices
- Implement VERP for accurate bounce tracking and automated processing
- Suppress hard bounces immediately - never retry permanent failures
- Retry soft bounces strategically - wait 1-24 hours between attempts
- Monitor bounce patterns - spikes indicate list quality issues
- Maintain suppression lists - sync across all sending infrastructure
- Set up webhooks/APIs - automate bounce processing with your ESP
- Regular list cleaning - validate emails before adding to lists
- Track bounce rates by segment - identify problematic list sources