Aerion

Aerion is an email client for Linux, published by 3DF. It is described as lightweight, indicating that the project aims at a small resource footprint rather than a broad feature set covering calendars, task lists, or groupware integration.

The client targets Linux desktops. No builds for Windows, macOS, Android, or iOS are described in the available facts, so users on those systems would need an alternative. As a desktop mail client, it is intended to be configured against existing mail accounts rather than to provide a mail service of its own.

Aerion is released under the Apache-2.0 licence, so the source code may be studied, modified, and redistributed under the licence's conditions. The facts at hand do not specify which mail protocols, authentication methods, or encryption features are implemented; these should be checked against the project's documentation before migrating an existing mailbox.