Queues

Overview

The Queues page provides visibility into email delivery queues and allows administrative control over message flow. Messages waiting for delivery are organized into queues by destination domain and optionally by campaign.

unMTA provides three views of your queues:

You can view queues across an entire cluster or filter to a specific MTA using the selector in the top right.

Scheduled Queues

The Scheduled Queues tab shows all active delivery queues. Each queue represents messages destined for a specific domain, optionally grouped by campaign.

From any queue row, you can click the menu to suspend or bounce that specific queue.

Suspended Queues

Suspended queues have delivery temporarily paused. Messages remain in the queue but won't be processed until the suspension expires or is manually removed.

To resume delivery, click the trash icon to delete the suspension.

Bounced Queues

Bounced queues are being administratively cleared. Matching messages are immediately bounced and removed, and new messages arriving for the same destination are also bounced until the rule expires.

To stop bouncing new messages, click the trash icon to delete the bounce rule.

Suspending a Queue

Suspending a queue pauses delivery without discarding messages. Use this when you need to temporarily halt delivery—for example, during recipient server maintenance or while investigating delivery issues.

Configuration

How to Suspend

From a scheduled queue:

1. In the Scheduled Queues tab, click the menu icon on a queue row
2. Select Suspend [domain]
3. Adjust duration and enter a reason
4. Click Suspend

For any domain:

1. Click Options in the top right
2. Select Suspend a Queue
3. Enter the domain (and optionally campaign)
4. Set duration and reason
5. Click Suspend

Suspension Behavior

• Messages remain queued but delivery attempts stop immediately
• The suspension applies to the entire cluster or selected MTA
• Suspension auto-expires after the specified duration
• You can manually delete the suspension to resume delivery early

Bouncing a Queue

Bouncing a queue permanently discards matching messages. Each bounced message generates an AdminBounce event in your logs (unless logging is suppressed).

Configuration

How to Bounce

From a scheduled queue:

1. In the Scheduled Queues tab, click the menu icon on a queue row
2. Select Bounce [domain]
3. Adjust duration and enter a reason
4. Optionally enable Suppress logging
5. Click Bounce

For any domain:

1. Click Options in the top right
2. Select Bounce a Queue
3. Enter the domain (and optionally campaign)
4. Set duration and reason
5. Click Bounce

Bounce Behavior

• Existing messages in matching queues are immediately bounced and removed
• New messages arriving during the duration are also bounced
• Each bounced message generates an AdminBounce event (unless suppressed)
• The bounce rule auto-expires after the specified duration
• You can manually delete the bounce rule to stop bouncing new messages

Removing Suspensions and Bounces

Removing a Suspension

1. Navigate to the Suspended Queues tab
2. Find the suspension you want to remove
3. Click the trash icon on that row
4. Delivery resumes immediately for the affected queue

Removing a Bounce Rule

1. Navigate to the Bounced Queues tab
2. Find the bounce rule you want to remove
3. Click the trash icon on that row
4. New messages will no longer be bounced (already bounced messages are gone)

Best Practices

When to Suspend

• Temporary delivery issues — Pause while a recipient server is experiencing problems
• Investigation — Hold messages while investigating high bounce rates
• Coordination — Pause delivery while coordinating timing with a recipient domain
• Maintenance — Halt delivery during your own maintenance windows

When to Bounce

• Invalid domains — Clear messages for domains confirmed as invalid or abandoned
• Recipient request — Honor requests to remove all pending messages
• Business decision — Stop all delivery to a domain based on policy
• Cleanup — Clear test or unwanted messages from queues

Duration Guidelines

Logging Considerations

• Keep logging enabled for audit trails unless you have a specific reason not to
• Suppress logging only for high-volume bounces where individual records aren't needed
• AdminBounce events are valuable for tracking what was removed and why