The Drupal 8 version of Mailhandler is based on Inmail module and takes mail (usually from an IMAP mailbox) and imports it as whatever type of content you choose. Beside the configured content type, you can specify the content type directly in your email subject. It enables you to select different authentication methods and mail analyzers as well.
Mailhandler Comment is a submodule that allows you to post comments by email.
Mailhandler includes a demo module to help you get started.