Bounce Rules
Bounces are categorized as Soft (temporary delivery errors) or Hard (permanent delivery issues). Each Internet Service Provider (ISP) reports bounces uniquely. Mumara allows you to create custom rules for classifying bounces based on their codes and errors.
Overview
Bounce rules analyze bounce messages and classify them:
+------------------+ +------------------+ +------------------+
| BOUNCE MESSAGE | ---> | MATCH RULES | ---> | CLASSIFICATION |
| (from mailbox) | | (in order) | | (soft/hard) |
+------------------+ +------------------+ +------------------+
|
+-----------------+-----------------+
| | |
v v v
+----------------+ +----------------+ +----------------+
| SOFT BOUNCE | | HARD BOUNCE | | EXCLUDE |
| Track count | | Flag contact | | No action |
| Keep sending | | Stop emails | | |
+----------------+ +----------------+ +----------------+
Rules can be reordered by drag-and-drop. They are processed sequentially based on the sorting order—the first matching rule is applied.
Why Bounce Rules Matter
Accurate Classification
- Distinguish temporary from permanent - Different actions for different bounces
- Reduce false positives - Don't suppress valid contacts for temporary issues
- Improve accuracy - Custom rules for your sending environment
List Quality
- Stop emailing invalid addresses - Hard bounced contacts won't receive further emails
- Preserve valid contacts - Soft bounces continue to receive emails as issues may resolve
- Maintain deliverability - Clean lists improve sender reputation
Customization
- Handle ISP-specific responses - Different providers use different codes
- Exclude test bounces - Don't process internal test failures
- Match your business rules - Customize based on your needs
Viewing Bounce Rules
Navigate to Setup → Bounce Rules to view all configured rules.
Page Features
- Add New button to create a rule
- Re-Sync Default Bounce Rules button to sync with latest defaults
- Reset to Default Bounce Rules button to restore factory rules
- Drag handle (≡) on each row to reorder rules
Table Columns
| Column | Description |
|---|---|
| (Drag Handle) | ≡ icon to drag and reorder rules |
| Bounce Rule Name | Name of the rule |
| Bounce Reason | Reason condition (if set) |
| Bounce Description | Description condition (if set) |
| Bounce Code | Code condition (if set) |
| Bounce | Classification: Soft, Hard, or Exclude from |
| Status | Active/Inactive toggle |
| Actions | Edit and Delete icons |
Rule Types
| Classification | Description | Contact Action |
|---|---|---|
| Soft | Temporary delivery failure | Track count, continue sending |
| Hard | Permanent delivery failure | Flag contact, stop all emails |
| Exclude from | Ignore this bounce | No action taken |
Understanding Bounce Types
Soft Bounces
Temporary delivery failures that may resolve:
| Example | Description |
|---|---|
| Mailbox full | Recipient's inbox is at capacity |
| Server unavailable | Temporary mail server issues |
| Rate limited | Too many emails sent too quickly |
| Greylisting | Temporary rejection for spam prevention |
Default action: Track the bounce count. Mumara continues to send emails to soft bounced contacts, as the issue may resolve on its own.
Contacts with soft bounces will continue to receive emails. The bounce is recorded for tracking purposes, but delivery attempts continue since the issue is temporary.
Hard Bounces
Permanent delivery failures that won't resolve:
| Example | Description |
|---|---|
| User unknown | Email address doesn't exist |
| Domain not found | Domain has no mail server |
| Permanently blocked | Recipient server blocks sender |
| Invalid address | Address format is invalid |
Default action: Flag the contact. Hard bounced contacts will not receive any further emails from the system.
Contacts with hard bounces are permanently flagged and will not receive any further emails from Mumara. This protects your sender reputation by preventing repeated delivery attempts to invalid addresses.
Exclude from Processing
Bounces that should be ignored:
| Example | Description |
|---|---|
| Auto-replies | Out-of-office responses |
| Challenge-response | CAPTCHA verification requests |
| Test bounces | Internal testing failures |
| System messages | Server status notifications |
Default action: Ignore, don't update contact status.
Reordering Rules
Rules are processed in the order they appear in the list. The first matching rule is applied.
How to Reorder
- Locate the ≡ (drag handle) icon on the left of a rule
- Click and hold the drag handle
- Drag the rule to the desired position
- Release to save the new order
Place more specific rules higher in the list. General catch-all rules should be at the bottom.
Global Rule
The Global Rule at the top is a default catch-all rule. It does not have a drag handle and remains at the top of the list.
Creating a Bounce Rule
Navigate to Setup → Bounce Rules and click Add New.
Rule Criteria
Status
Toggle to enable or disable the rule.
Rule Name
Enter a descriptive name for the rule.
Examples:
- "Gmail - User Unknown"
- "Office 365 - Mailbox Full"
- "Greylisting - Temporary Rejection"
- "Auto-Reply - Ignore"
Conditions
Configure conditions that must match for the rule to apply. Multiple conditions use AND logic—all conditions must match.
Adding a Condition
Each condition has three parts:
| Part | Description | Options |
|---|---|---|
| Field | What to match against | Bounce Code, Bounce Reason, Bounce Description |
| Operator | How to match | Is, Contains |
| Value | The value to match | Text or code to look for |
Condition Fields
| Field | Description | Example Values |
|---|---|---|
| Bounce Code | SMTP error code | 550, 5.1.1, 4.2.2, 5.0.0 |
| Bounce Reason | Reason category | user unknown, mailbox full, blocked |
| Bounce Description | Extended error message | The email account does not exist |
Adding Multiple Conditions
- Configure the first condition
- Click + Add Condition button
- Configure the next condition (connected with "and")
- Repeat as needed
All conditions are joined with AND logic—all must match for the rule to apply.
Removing a Condition
Click the X button next to a condition to remove it.
Classification
Classify as
Select how matching bounces should be classified:
| Option | Description |
|---|---|
| Hard Bounce | Permanent failure - suppress contact |
| Soft Bounce | Temporary failure - track and retry |
| Exclude from processing | Ignore - don't update contact |
Saving the Rule
Click Save to create or update the rule.
Click Cancel to discard changes.
Default Bounce Rules
Mumara includes pre-configured rules for common bounce scenarios.
Re-Sync Default Bounce Rules
Synchronize with the latest default rules without removing custom rules:
- Click Re-Sync Default Bounce Rules
- New default rules are added
- Existing default rules are updated
- Custom rules are preserved
Reset to Default Bounce Rules
Restore all rules to factory defaults:
- Click Reset to Default Bounce Rules
- Confirm the reset
- All rules are replaced with factory defaults
Resetting removes all custom rules. This action cannot be undone.
Common Default Rules
| Rule Name | Bounce Code | Classification |
|---|---|---|
| Global Rule | Any | Soft |
| Address does not exist | 5.0.0 | Hard |
| Other address status | 5.1.0 | Hard |
| Bad destination mailbox | 5.1.1 | Hard |
| Bad destination system | 5.1.2 | Hard |
| Bad destination mailbox syntax | 5.1.3 | Hard |
| Destination mailbox address ambiguous | 5.1.4 | Hard |
| The email account is over quota | 4.2.2 | Soft |
| Security features not supported | 5.7.4 | Hard |
Managing Bounce Rules
Editing a Rule
- Click the Edit icon (pencil) on a rule
- Modify the rule criteria
- Click Save
Deleting a Rule
- Click the Delete icon (trash) on a rule
- Confirm deletion
Changing Status
Toggle the Status switch directly in the list to enable or disable a rule.
Example Rules
Hard Bounce: User Unknown
Rule Name: User Unknown - Hard Bounce
Conditions:
- Bounce Code | Is | 550
- Bounce Reason | Contains | user unknown
Classify as: Hard Bounce
Hard Bounce: Invalid Domain
Rule Name: Invalid Domain - Hard Bounce
Conditions:
- Bounce Code | Is | 5.1.2
- Bounce Description | Contains | domain not found
Classify as: Hard Bounce
Soft Bounce: Mailbox Full
Rule Name: Mailbox Full - Soft Bounce
Conditions:
- Bounce Code | Is | 4.2.2
- Bounce Reason | Contains | quota
Classify as: Soft Bounce
Soft Bounce: Server Busy
Rule Name: Server Busy - Soft Bounce
Conditions:
- Bounce Code | Is | 421
Classify as: Soft Bounce
Exclude: Auto-Reply
Rule Name: Auto-Reply - Ignore
Conditions:
- Bounce Reason | Contains | auto-reply
Classify as: Exclude from processing
Exclude: Out of Office
Rule Name: Out of Office - Ignore
Conditions:
- Bounce Description | Contains | out of office
Classify as: Exclude from processing
Common Bounce Codes
4xx Codes (Soft Bounces)
| Code | Description |
|---|---|
| 421 | Service temporarily unavailable |
| 450 | Mailbox unavailable (temporary) |
| 451 | Local error in processing |
| 452 | Insufficient storage |
5xx Codes (Hard Bounces)
| Code | Description |
|---|---|
| 500 | Syntax error |
| 550 | Mailbox unavailable (permanent) |
| 551 | User not local |
| 552 | Message size exceeded |
| 553 | Mailbox name not allowed |
| 554 | Transaction failed |
Enhanced Status Codes
| Code | Description |
|---|---|
| 5.0.0 | Other undefined status |
| 5.1.0 | Other address status |
| 5.1.1 | Bad destination mailbox address |
| 5.1.2 | Bad destination system address |
| 5.1.3 | Bad destination mailbox address syntax |
| 5.1.4 | Destination mailbox address ambiguous |
| 5.2.1 | Mailbox disabled |
| 5.2.2 | Mailbox full |
| 5.7.1 | Delivery not authorized |
| 4.2.2 | Mailbox full (temporary) |
Best Practices
Rule Design
- Be specific - Target exact scenarios to avoid false positives
- Use multiple conditions - Combine code + reason for accuracy
- Test thoroughly - Verify rules work as expected
- Use descriptive names - Make rules easy to identify
Rule Organization
- Order by specificity - Most specific rules first
- Group by provider - Organize ISP-specific rules together
- Review regularly - Update rules as ISPs change responses
- Keep it simple - Fewer, well-designed rules are better
Monitoring
- Check bounce reports - Verify classification accuracy
- Review unclassified - Add rules for new bounce patterns
- Monitor soft bounces - Ensure thresholds are appropriate
- Track false positives - Adjust rules causing issues
Troubleshooting
Bounces Not Classified
Possible causes:
- No matching rule exists
- Rule conditions too specific
- Rule is disabled
Solutions:
- Review bounce message details
- Create rule for new pattern
- Broaden condition operators
- Enable disabled rules
Wrong Classification
Possible causes:
- Rule conditions match incorrectly
- Rule priority is wrong
- Multiple rules matching
Solutions:
- Review rule conditions
- Reorder rules (drag-and-drop)
- Make conditions more specific
- Check for conflicting rules
Soft Bounces Being Suppressed
Possible causes:
- Classified as hard bounce
- Soft bounce threshold reached
- Rule misconfigured
Solutions:
- Verify rule classification
- Check soft bounce threshold settings
- Review rule conditions
Hard Bounces Not Suppressed
Possible causes:
- Classified as soft bounce
- Rule not matching
- Processing disabled
Solutions:
- Verify rule classification
- Check rule conditions
- Ensure bounce processing is enabled
Next Steps
- Bounce Addresses - Configure bounce mailboxes
- Sending Nodes - Set up SMTP with bounce handling
- Suppression - View suppressed contacts