How to add List-Unsubscribe Header

[Dolzen]

Hello guys, I'm pretty new at this stuff but I've got Roundcube working, now I want to add a List-unsubscribe Header, I don't know what I'm doing wrong I have the "show_additional_headers" and the "additional_message_headers" plugins enabled but I cannot find where it is supposed to be the settings to enable or add the new custom header, I do not know what I'm missing.

Any help would be appreciated, thanks.

[SKaero]

You add the headers in the Roundcube config, see the config.inc.dist in the additional_message_headers plugin folder for examples.