@delta - Encrypted messenger app powered by email
@thunderbird@mastodon.online (main) & @thunderbird@tilvids.com (videos) - Free open source email & communications suite
@EvolutionGnome - Free open source email, contacts, calendars, tasks, notes software
@WorfEmail - Lieutenant Worf is sending emails

INDEPENDENT EMAIL PROVIDERS
@fastmail - ...in Australia
@hellomailo - ...in France (in French)
@Tutanota - ...in Germany
@mailbox_org - ...in Germany (in German)
@runbox - ...in Norway