In current version, plugin doesn't allow to set the notification content.
In my project, I use this plugin not only to indicate if CI job was deleted, but also if CI job was shelved (see https://wiki.jenkins-ci.org/display/JENKINS/Shelve+Project+Plugin) because Jenkins recognizes shelved jobs as deleted.
But in this case one can't understand if CI job was deleted or shelved. So the ability to set custom Email message might help.
Thanks.