We use an email service to send users a message when a changeset is labeled. We use e.g. "D" as Discarded, for labeling this changeset as bad.
Currently you can't get the owner of the labeled changeset from the environment variable in the after-mklabel trigger. Also you can't get the id of the changeset.
Workaround would be, to use a cm find label with the given label name and repository to fand the label and the changeset id to get the owner of the changeset. I don't know why but this is currently not working inside of our trigger logic.

So it would be nice to add the changeset owner and changeset id as variable .