Puma binding to 127.0.0.1:5000 instead of 0.0.0.0:5000 in Postal 3.3.4 Docker deployment

[Ouniit03]

Environment
Postal Version: 3.3.4
Deployment Method: Docker Compose / docker run
Image: ghcr.io/postalserver/postal:3.3.4
OS: Linux #17~24.04.2-Ubuntu
Docker Version: Docker version 26.1.3
Relevant Configuration
postal.yml (located at /opt/postal/config/postal.yml):

version: 2
web:
bind: "0.0.0.0:5000"
protocol: http

docker-compose.yml (postal-web section):

services:
postal-web:
image: ghcr.io/postalserver/postal:3.3.4
ports:
- "5000:5000"
volumes:
- type: bind
source: /opt/postal/config
target: /config
bind:
create_host_path: true
depends_on:
- postal-mariadb
environment:
POSTAL_WEB_BIND: "0.0.0.0:5000"
WEB_BIND: "0.0.0.0:5000"
entrypoint: ["postal"]
command: ["web-server", "--config", "/config/postal.yml"]

Troubleshooting Steps Taken
1.Configuration Verification:
Verified that the configuration file is correctly mounted inside the container by running cat /config/postal.yml, which confirmed the web.bind is set to "0.0.0.0:5000".

2.Environment Variables Check:
Inside the container, env | grep -i 'WEB_BIND|POSTAL_WEB_BIND' shows both variables set to 0.0.0.0:5000.

3.Docker Port Mapping:
docker ps confirms the host port mapping as 0.0.0.0:5000->5000/tcp.

4.Direct Container Test:
Ran the following command to test directly:

docker run -it --rm -p 5000:5000 -v /opt/postal/config:/config ghcr.io/postalserver/postal:3.3.4 postal web-server --config /config/postal.yml

However, the logs show:

**Loading config from /config/postal.yml
Puma starting in single mode...

• Listening on http://127.0.0.1:5000**

indicating that Puma still binds to 127.0.0.1:5000 instead of 0.0.0.0:5000.

5.Alternate Parameter Attempts:
I attempted adding command-line options like --host 0.0.0.0 --port 5000, but the logs still show Puma binding to 127.0.0.1:5000.

6.Port Mapping Check with Other Images:
I confirmed that Docker's port mapping works correctly by testing with an nginx container on the same port.

Problem Description:
Even though both postal.yml and docker-compose.yml (and the corresponding environment variables) are set to bind to 0.0.0.0:5000, Puma still ends up binding to 127.0.0.1:5000 within the container. This causes external connections (via Docker port mapping) to fail. Is this behavior a known issue or bug in Postal 3.3.4? Are there any recommended workarounds or fixes?

Thanks for your assistance!

[willpower232]

I don't think you should supply both a config file and environment variables, that is probably confusing things.

The config file is a bit different to how you have it, have a look at

postal/doc/config/yaml.yml

Lines 37 to 41 in fd3c7cc

	web_server:
	# The default port the web server should listen on unless overriden by the PORT environment variable
	default_port: 5000
	# The default bind address the web server should listen on unless overriden by the BIND_ADDRESS environment variable
	default_bind_address: 127.0.0.1

[Ouniit03]

Thanks for your response! I'll try updating postal.yml and see if it works.