cant run an smtp docker container on linux AMI

Question

Hi, 
i'm trying to run postfix/dovcot containers using docker-compose on a new Linux AMI based vm i just created. 
docker daemon issues an error: "Error response from daemon: driver failed programming external connectivity on endpoint  (582c7551d1c87e6131cb153b1dee9f9c1d0bd5ea1eaedfe070d7952276547569): Error starting userland proxy: listen tcp4 0.0.0.0:25: bind: address already in use"

indeed ,running 
```
sudo lsof -i:25 |grep LISTEN
```
shows that the port is used. this is the output :
```
master  3038 root   13u  IPv4  17945      0t0  TCP localhost:smtp (LISTEN)
```

What am i missing here ? why is that port taken ? i read some comments on the net saying that Amazon prevent using port 25 by default - is that the case here ?
Thanks in advance
Sivan

Accepted Answer

So i found out that this AMI comes with postfix installed and enabled , i did not know postfix is installed by default.
i simply had to disable and stop the service.
I found this by mistake while running some ```ps aux``` commands ,grepping for pids. 
what i  did was:
``` 
sudo systemctl stop postfix
sudo systemctl disable postfix # so that postfix wont reload when my vm restarts
```

cant run an smtp docker container on linux AMI

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