Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Mailinator - Any Inbox. Any Time.
Keybase Chat - End-to-end encrypted chat built into Keybase
TempMail.altmails - Disposable temporary email addresses
Crypho - End-to-end-encrypted messaging and file sharing
Harakirimail - Harakirimail is a free disposable email service. Just send email to anythingyouwant@harakirimail.