One example where I had issues with Mailhog was that the docker images was very bloated 138.8MB[0], there was a PR that should have brought it back to 7MB or something but it was never merged.

And not sure about this, but at least for docker, the included certificates can become outdated if not frequently rebuilt, and since Mailhog is software used when testing, being able to spin up a ready-to-use sandboxed instance is very useful.

[0] https://hub.docker.com/r/mailhog/mailhog/tags