No specific info about version 11.4. Please visit the main page of MailSteward on Mac Informer.
It copies Mail.app message properties to the clipboard for further saving.
Eudora Mailbox Cleaner is a simple drag'n'drop application.
It removes duplicate messages from the current selection in Apple Mail.
Trash mail duplicates moves duplicate messages to Mail trash.
It is a script that creates to-do items from Mail messages.