Problem: a) Protonmail Bridge cannot listen to IP other than `127.0.0.1`, and b) Discourse in a Docker container cannot send SMTP requests to `127.0.0.1` of the host machine.
Solution: We configure it to send to `172.17.0.1` (the Docker’s bridge IP on the host machine), and then redirect to `127.0.0.1`, on which the Protonmail Bridge is listening.
We do it with using Socat.
### How To
Start by installing Socat:
`apt install socat`
We will run Socat as a service. Create service file:
`nano /etc/systemd/system/protonsocat.service`
… and put the following content in it:
```plaintext
[Unit]
Description=Socat Bridge ProtonMail/Discourse
After=protonbridge.service,docker.service
ReloadPropagatedFrom=docker.service
[Service]
ExecStart=socat -d -d -lm TCP4-LISTEN:1026,fork,reuseaddr,so-bindtodevice=docker0,range=172.17.0.0/24 TCP4:127.0.0.1:1025
Restart=always
RestartSec=2
[Install]
WantedBy=multi-user.target
```
Notes:
- We configured Socat to listen to all IPs `172.17.0.0/24`, port `1026`, and redirect the traffic to `127.0.0.1:1025`, where Protonmail Bridge is listening
- Example from Socat documentation: [socat](http://www.dest-unreach.org/socat/doc/socat.html#EXAMPLE_OPTION_BIND_TCP4)
- -d -d will print the fatal, error, warning, and notice messages; you may not want that much detail logged
Next, start the service:
`systemctl start protonsocat`
Check that it is running:
`systemctl status protonsocat`
And automatically get it to start on boot:
`systemctl enable protonsocat`
Done! Now, configure Discourse `app.yml` and rebuild:
```plaintext
DISCOURSE_SMTP_ADDRESS: 172.17.0.1
DISCOURSE_SMTP_PORT: 1026
DISCOURSE_SMTP_USER_NAME:
DISCOURSE_SMTP_PASSWORD: ""
DISCOURSE_SMTP_ENABLE_START_TLS: true
DISCOURSE_SMTP_DOMAIN:
DISCOURSE_NOTIFICATION_EMAIL:
```
---
Hi @meglio
I cannot find protonbridge.service so I replaced it with protonmail.service
But seems there’s issue with the format After=protonbridge.service,docker.service
---
Hi @meglio This seems to be giving me an error
After the initial sysctl commands
```plaintext
root@ip-172-31-0-166:/var/discourse# systemctl status protonsocat.service
● protonsocat.service - Socat Bridge ProtonMail/Discourse
Loaded: loaded (/etc/systemd/system/protonsocat.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2022-12-18 20:58:18 UTC; 25s ago
Main PID: 2020962 (socat)
Tasks: 1 (limit: 1143)
Memory: 2.0M
CPU: 4ms
CGroup: /system.slice/protonsocat.service
└─2020962 socat -d -d -lm TCP4-LISTEN:1026,fork,reuseaddr,so-bindtodevice=docker0,range=172.17.0.0/24 TCP4:127.0.0.1:1025
Dec 18 20:58:18 ip-172-31-0-166 systemd[1]: Started Socat Bridge ProtonMail/Discourse.
Dec 18 20:58:18 ip-172-31-0-166 socat[2020962]: 2022/12/18 20:58:18 socat[2020962] W ioctl(5, IOCTL_VM_SOCKETS_GET_LOCAL_CID, ...): Inappropriate ioctl for device
Dec 18 20:58:18 ip-172-31-0-166 socat[2020962]: N listening on AF=2 0.0.0.0:1026
**Dec 18 20:58:42 ip-172-31-0-166 systemd[1]: /etc/systemd/system/protonsocat.service:3: Failed to add dependency on protonbridge.service,docker.service, ignoring: Invalid argument**
```
Also when running the ./discourse-doctor I am getting error as
```plaintext
==================== MAIL TEST ====================
For a robust test, get an address from http://www.mail-tester.com/
Or just send a test message to yourself.
Email address for mail test? ('n' to skip) [[REDACTED]@proton.me]:
Sending mail to [REDACTED]@proton.me. . .
SAM: sudo docker exec -w /var/www/discourse -i app rake emails:test[[REDACTED]@proton.me]
Testing sending to [REDACTED]@proton.me using 172.17.0.1:1026, username:[REDACTED]@proton.me with plain auth.
======================================== ERROR ========================================
UNEXPECTED ERROR
**end of file reached**
====================================== SOLUTION =======================================
This is not a common error. No recommended solution exists!
Please report the exact error message above to https://meta.discourse.org/
(And a solution, if you find one!)
```
Any pointers would be appreciated and would be helpful!
Thank you.
---