Bounce Classification Codes and Definitions

Overview

PXME’s Email Bounce Classification helps you diagnose why emails fail and take corrective action to improve deliverability. By categorizing bounces (invalid addresses, full mailboxes, DMARC misalignment, sender reputation issues, etc.), you gain visibility into root causes and tools to ensure messages reach patient families consistently.

Key Features and Benefits

• Bounce Summary Overview – Track permanent bounces, bounce rates, delivery percentages, and ISP/ESP blocks.

• Detailed Bounce Classification – View failures broken down by provider, error category, and error code.

• ESP/ISP Block Tracking – Identify Gmail, Outlook, or Yahoo blocks due to policy or reputation.

• Advanced Filtering – Drill down by domain, IP, message type, or error code.

• Actionable Troubleshooting – Linked definitions and fixes guide you to resolve DNS, blacklist, or content issues.

How to Use Bounce Classification

Step 1: Access the Dashboard

• Go to Settings > Email Services > Bounce Classification.

Step 2: Review Metrics

• Check totals for permanent bounces, bounce rates, and delivery rates.

Step 3: Apply Filters

• Refine by domain, ESP, bounce category, or code.

Step 4: Analyze Bounce Details

• Click into codes (e.g., 550, 5.7.509) for the exact error description and recommended fix.

Step 5: Resolve Issues

• Follow guidance such as updating DNS records, removing invalid contacts, or contacting ESP support.

Step 6: Monitor Blocks

• Identify ISP/ESP blocks and use the provided links to request delisting or fix policy violations.

Common Bounce Categories

1. Blocked

• Codes: 554, 5.2.3

• Cause: Email blocked by recipient’s policies (mailbox quotas, size limits, org rules).

• Fix: Reduce message size, confirm limits, contact recipient admin.

2. DMARC Failures

• Codes: 509, 550, 553, 554, 555

• Cause: “From” domain misaligned with SPF/DKIM.

• Fix: Ensure SPF/DKIM records align with your From Address.

3. Invalid Address

• Codes: 450, 500, 501, 550, 551, 552, 553, 554

• Cause: Nonexistent, inactive, or mistyped address.

• Fix: Validate emails before sending; clean lists.

4. Mailbox Issues

• Codes: 450, 452, 498, 550, 552, 553, 554

• Cause: Disabled or inactive mailbox.

• Fix: Verify account validity; remove inactive contacts.

5. Mailbox Full

• Codes: 452, 550, 552

• Cause: Recipient inbox storage exceeded.

• Fix: Retry later or ask recipient to clear space.

6. Rate Limit

• Codes: 221, 550, 554

• Cause: Sending too many emails too quickly.

• Fix: Throttle sending speed or use smaller batches.

7. Recipient Errors

• Codes: 450, 502, 530, 541, 550–579, 701

• Cause: Recipient’s server restrictions (e.g., blocks external mail, expired retries).

• Fix: Contact recipient or validate DNS/routing records.

8. Rejection

• Codes: 450, 501, 533, 550, 553, 554

• Cause: Missing DNS, oversized message, loops, unsupported config.

• Fix: Verify DNS, reduce size, check loop prevention.

9. Sender Reputation

• Cause: Poor IP/domain reputation or blacklists.

• Fix:

  • Check reputation via Google Postmaster Tools and Microsoft SNDS.

  • Warm up IPs gradually.

  • Avoid spammy content.

  • Always include unsubscribe links.

FAQs

Q1: What is Bounce Classification?
It categorizes bounced emails to help you resolve issues and improve deliverability.

Q2: Where do I find it?
In Settings > Email Services > Bounce Classification.

Q3: What are the main categories?
Invalid Address, Mailbox Full, DMARC/Authentication Issues, Sender Reputation, and Blocks.

Q4: Can I filter bounce results?
Yes. Filter by domain, provider, error code, or IP.

Q5: What insights does the summary provide?
Bounce totals, rates, ESP/ISP block detection, and delivery percentages.

Q6: How do I fix bounce issues?
Follow PXME’s recommended steps: clean lists, fix DNS, slow sending, or request delisting.