- https://en.wikipedia.org/wiki/Roundcube
- https://github.com/roundcube/roundcubemail/issues/1635
- https://github.com/roundcube/roundcubemail/issues/5133
It is not really obvious how to undelete messages with Roundcube. But it works:
- click on the icon!
- do not search for “Mark as undeleted“!