Mail Queue¶
The Mail Queue shows the active Postfix delivery queue — messages waiting for delivery due to temporary errors, network issues, or greylisting.
Difference from Quarantine
The mail queue shows the active delivery queue (deferred, active). The quarantine (hold queue) is a separate area managed under Quarantine.
Queue Overview¶
| Column | Description |
|---|---|
| Queue ID | Postfix queue ID (unique per message per node) |
| Size | Message size in bytes |
| Arrival | Timestamp of first delivery attempt |
| Sender | Envelope-From address |
| Recipients | Destination addresses |
| Error | Last delivery error (e.g. Connection refused) |
| Node | Cluster node |
Actions¶
Individual Messages¶
- Retry (Flush) — Force immediate re-delivery attempt
- Delete — Remove message from queue (no bounce)
- Force Bounce — Send DSN to sender and delete mail
Flush All¶
Immediately attempt delivery of all messages in the active queue. Useful after a temporary network outage.
Domain Flush¶
Immediately deliver only messages for a specific recipient domain. Enter the domain in the filter field and click Flush.
Common Error Causes¶
| Error | Cause | Solution |
|---|---|---|
Connection refused |
Destination mail server unreachable | Check network/firewall |
Host not found |
DNS issue for destination domain | Check DNS resolution |
Greylisting |
Sender is being temporarily rejected | Wait or whitelist sender |
Message size exceeds limit |
Message too large | Check size limit in Mail Configuration |
Too many connections |
Rate limit exceeded | Check rate limit settings |
Queue Monitoring¶
For continuous queue monitoring, an external monitoring tool (e.g. Checkmk/Nagios) on the Postfix queue counter is recommended: