Mailcow Docker: mailcowdockerized-unbound-mailcow-1 is unhealthy quite often

hirschnase

Hello Community,

my unbound Docker container does restart once or twice every day. This is what I see in the docker logs output:

2026-03-12 10:40:27: Healthcheck: Too many DNS failures (1 failures allowed, you got 2 failures), marking Healthcheck as unhealthy... 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 1 for github.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 2 for github.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 3 for github.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution not possible after 3 attempts for github.com... Gave up! 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 1 for hub.docker.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 2 for hub.docker.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution Failed on attempt 3 for hub.docker.com! Trying again... 2026-03-12 10:41:03: Healthcheck: DNS Resolution not possible after 3 attempts for hub.docker.com... Gave up! 2026-03-12 10:41:03: Healthcheck: Too many DNS failures (1 failures allowed, you got 2 failures), marking Healthcheck as unhealthy... 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 1 for github.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 2 for github.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 3 for github.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution not possible after 3 attempts for github.com... Gave up! 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 1 for hub.docker.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 2 for hub.docker.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution Failed on attempt 3 for hub.docker.com! Trying again... 2026-03-12 10:41:39: Healthcheck: DNS Resolution not possible after 3 attempts for hub.docker.com... Gave up! 2026-03-12 10:41:39: Healthcheck: Too many DNS failures (1 failures allowed, you got 2 failures), marking Healthcheck as unhealthy... 2026-03-12 10:42:15: Healthcheck: DNS Resolution Failed on attempt 1 for github.com! Trying again... 2026-03-12 10:42:15: Healthcheck: DNS Resolution Failed on attempt 2 for github.com! Trying again... 2026-03-12 10:42:16: Healthcheck: DNS Resolution Failed on attempt 3 for github.com! Trying again... 2026-03-12 10:42:16: Healthcheck: DNS Resolution not possible after 3 attempts for github.com... Gave up! 2026-03-12 10:42:17: Healthcheck: DNS Resolution Failed on attempt 1 for hub.docker.com! Trying again... 2026-03-12 10:42:17: Healthcheck: DNS Resolution Failed on attempt 2 for hub.docker.com! Trying again... 2026-03-12 10:42:17: Healthcheck: DNS Resolution Failed on attempt 3 for hub.docker.com! Trying again... 2026-03-12 10:42:17: Healthcheck: DNS Resolution not possible after 3 attempts for hub.docker.com... Gave up! 2026-03-12 10:42:17: Healthcheck: Too many DNS failures (1 failures allowed, you got 2 failures), marking Healthcheck as unhealthy... 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 1 for github.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 2 for github.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 3 for github.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution not possible after 3 attempts for github.com... Gave up! 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 1 for hub.docker.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 2 for hub.docker.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution Failed on attempt 3 for hub.docker.com! Trying again... 2026-03-12 10:42:53: Healthcheck: DNS Resolution not possible after 3 attempts for hub.docker.com... Gave up! 2026-03-12 10:42:53: Healthcheck: Too many DNS failures (1 failures allowed, you got 2 failures), marking Healthcheck as unhealthy...

When I exec into the container and do a “nslookup” manually, it works fine.
What can I do to fix this? Does anyone have an idea what the problem could be?

Thanks! Marc