https://news.ycombinator.com/item?id=19712437
https://sylpheed.sraoss.jp/en/
https://www.claws-mail.org/
https://www.postbox-inc.com/
https://freron.com/
https://gitlab.com/ambrevar/mu4e-conversation
https://ivelope.com/
http://www.memecode.com/scribe.php
