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K-9 Mail is looking for funding
Never heard of K-9, well nobody is perfect:
K-9 Mail is an open source email client focused on making it easy to chew through large volumes of email
Via:
https://k9mail.app/2021/02/14/K-9-Mail-is-looking-for-funding
Server run by the main developers of the project 
It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!