Tim Jacomb

There's also a couple of other fixes. You can change your preferences to not use the bundled one and somewhere you can set it at a project level (which appears...

There's nothing easy that I'm aware of currently, but this would be a good feature to add.

What's in your slack configuration file?

Looks like a problem with the mail address resolvers, if you remove that I expect it will work

Any chance you are running in docker and are hit by: https://github.com/jenkinsci/docker/issues/1193 ? If you use 2.309 does it work?

If you're doing a custom build all you need to do is add this: https://github.com/jenkinsci/docker/commit/e71180956b43b89b6cd3559db6922e0c47e7d574#diff-7891a6415ef795387fa7e9c8f2f5eee4dc1bb9291e6420b321132405ce15f56a Otherwise you can probably set the JVM flag `-Dfile.encoding=utf-8` as well as an alternative

Is there any error or logs?

Unlikely to happen, unless someone contribute it, but it's not an easy feature to do. Easily achieved with pipeline

Could probably just add it to the 'channel / member id' field and detect if it's an email address? or a separate field?

Please update your slack plugin that version is ancient Then follow the troubleshooting steps if there’s still an issue https://github.com/jenkinsci/slack-plugin/blob/master/README.md#troubleshooting-connection-failure