bemade-addons/mail_loop_prevention

Mail Loop Prevention

Overview

This module prevents communication loops that can occur when two mail servers auto-reply to each other indefinitely. This commonly happens with:

• Delivery receipt acknowledgements
• Out-of-office auto-replies
• Automated notification systems
• Email bounce handlers

How It Works

The module overrides mail.thread._message_create() to detect potential loops by:

1. Content Hashing: Creates a hash of message body and subject (unescapes HTML and normalizes whitespace)
2. Time Window Check: Looks for identical messages within a configurable time window (default: 48 hours)
3. Threshold Detection: Blocks messages if the number of identical messages exceeds a threshold (default: 3)
4. Smart Filtering: Only checks automated messages (notification, auto_comment, email types), never blocks user comments

Configuration

The module uses system parameters that can be configured via Settings > Technical > Parameters > System Parameters:

Parameter	Default	Valid Range	Description
mail_loop_prevention.enabled	True	True/False	Enable/disable loop prevention
mail_loop_prevention.time_window_hours	48	1 to 720	Time window in hours to check for duplicates (max 30 days)
mail_loop_prevention.max_identical_messages	3	2 to 100	Maximum identical messages allowed before blocking

Configuration Validation

The module validates all configuration parameters when they are set:

• enabled: Accepts True/False, 1/0, yes/no, on/off (case-insensitive)
• time_window_hours: Must be an integer between 1 and 720 (30 days)
• max_identical_messages: Must be an integer between 2 and 100

Invalid values will raise a ValidationError and prevent the parameter from being saved.

Example Scenario

Without this module:

Server A → Auto-reply to Server B
Server B → Auto-reply to Server A
Server A → Auto-reply to Server B
Server B → Auto-reply to Server A
... (infinite loop)

With this module:

Server A → Auto-reply to Server B (1st message - allowed)
Server B → Auto-reply to Server A (1st message - allowed)
Server A → Auto-reply to Server B (2nd message - allowed)
Server B → Auto-reply to Server A (2nd message - allowed)
Server A → Auto-reply to Server B (3rd message - allowed)
Server B → Auto-reply to Server A (3rd message - allowed)
Server A → Auto-reply to Server B (4th message - BLOCKED)

Technical Details

Message Types Checked

The module only checks these message types for loops:

• notification - System notifications
• auto_comment - Automated comments
• email - Email messages

Regular comment type messages (user posts) are never blocked.

Duplicate Detection

Messages are considered identical if they have the same:

• Body content (after unescaping HTML entities and normalizing whitespace)
• Subject line

Real-world loops send exactly the same message repeatedly, so direct content comparison is sufficient.

Performance Considerations

• Only checks messages within the configured time window
• Uses SHA-256 hashing for efficient comparison
• Minimal database queries (uses existing message_ids relation)

Testing

Run the test suite:

odoo-bin -c odoo.conf -d test_db -i mail_loop_prevention --test-enable --stop-after-init

Troubleshooting

Legitimate messages being blocked

If legitimate automated messages are being blocked:

1. Check the logs for "Loop prevention: Blocking duplicate message" warnings
2. Increase mail_loop_prevention.max_identical_messages threshold
3. Reduce mail_loop_prevention.time_window_hours if the messages are spread over time
4. Temporarily disable with mail_loop_prevention.enabled = False to diagnose

Loops still occurring

If loops are still happening:

1. Verify the module is installed and enabled
2. Check that mail_loop_prevention.enabled = True
3. Reduce the max_identical_messages threshold
4. Check if the messages have varying content (different subjects/bodies)

License

AGPL-3.0 or later (http://www.gnu.org/licenses/agpl)