Mailbutler GmbH (https://www.mailbutler.io) has upgraded their email extension for Apple Mail and Gmail users.
The extension acts as a “Swiss army knife” for emails while integrating into the native interfaces of the email apps. The Mailbutler upgrade sports a revamped interface and new functions.
MailButler requires macOS 10.10 or higher. A demo is available for download; registration is $8.95