Shoutrrr e-mail notifications using host postfix installation

[porchy13]

I try to use the new configuration-url, but I struggle to get it running.

I am using postfix, configured as satellite, to send notifications from Watchtower. postfix is installed on the host, so I configured Watchtower's network as host and contact postfix, using the localhost address. I also use the users as from and to addresses.

- WATCHTOWER_NOTIFICATIONS=email
- WATCHTOWER_NOTIFICATION_EMAIL_FROM=root
- WATCHTOWER_NOTIFICATION_EMAIL_TO=root
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER=localhost
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PORT=25
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER_TLS_SKIP_VERIFY=true

I tried to replicate the configuration above, using the configuration-url, as shown below.

- WATCHTOWER_NOTIFICATION_URL=smtp://localhost/?fromaddress=root&toaddress=root&encryption=None&usestarttls=no

But the notifications system refuse to start, as stated by the following error.

watchtower-1  | time="2026-07-24T07:38:09Z" level=fatal msg="Failed to initialize Shoutrrr notifications" error="creating sender with options for URLs [smtp://localhost/?fromaddress=root&toaddress=root&encryption=None&usestarttls=no]: error initializing router services: smtp: failed to initialize service" notify=no

I've also tried various alternatives :

• About the SMTP address : network mode changed to bridge, and/or using host.docker.internal, adding the port number, adding a user, without password.
• About the from and to addresses : using the user's e-mail address (root@<redacted>).

None of the tested alternatives worked.

Does anyone have a solution for me ?

Thanks in advance.

[janitor-of-code]

it is toadresses i.e. plural if I'm not mistaken

[janitor-of-code]

Tested it myself and it seems to lack error handling - after fixing that typo I got proper errors about which part of my mail config still fails

[porchy13]

I had not noticed it was plural 🙈

Thanks for your quick answer, it works for me, now.