This is GNU Mailman, a mailing list management system. This metapackage depends on all components of the full Mailman3 suite:

* mailman3: The core Mailman3 delivery engine
* mailman3-web: Django project integrating Mailman3 postorius and hyperkitty
* python3-mailman-hyperkitty: Mailman3 server plugin for Hyperkitty archiver