> Source: [sk110856](https://support.checkpoint.com/results/sk/sk110856)

# sk110856 - Mail is stuck in the postfix queue

| Property | Value |
|----------|-------|
| Solution ID | sk110856 |
| Date Created | 2016-04-05 |
| Last Modified | 2016-04-13 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |
| OS | Gaia |

## Symptoms

- * Some e-mails do not arrive at their destination when Mail Transfer Agent (MTA) is enabled on the gateway.
* When checking the postfix queue, there are emails with "Unknown mail transport error".
* /opt/postfix/etc/postfix/main.cf shows no value for relayhost: relayhost = \[\]:0

## Cause

`/opt/postfix/etc/postfix/main.cf` is missing the configuration for relayhost:

*\[Expert@GW\]# grep relayhost /opt/postfix/etc/postfix/main.cf*   
*relayhost = \[\]:0*

```
The Postfix can't tell where to send the mail after it has finished processing.
This causes mail to remain in the queue.
```

### Example:

Example of mail being stuck in the postfix queue:

`[Expert@GW]:# /opt/postfix/usr/sbin/postqueue -p`  
`-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------`  
`<queue ID> <size> Day Mon ## HH:MM:SS <dlp-gw@domain.com>(unknown mail transport error)`  
`<queue ID> <size> Day Mon ## HH:MM:SS <dlp-gw@domain.com>(unknown mail transport error)`

## Solution

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