Prior to installing this plugin; IMAP Sync should be installed and avalaible at /usr/bin/imapsync
(https://github.com/imapsync/imapsync) - Shoutouts to @gilleslamiral for his excellent work.
To install; just run install.sh - that's it.
Plugin can be toggled using "Feature Manager" for specific packages.
Once installed, customers will see an option that says "Sync IMAP Account" under the Email section of cPanel.