Send Secure Document
 
Firefox Send lets you freely share files with end-to-end encryption via a link you can send to anyone that automatically expires in 1-7 days and after 1-100 downloads.  The link can be password protected.  No sign up or download required for files up to 1 GB.  Browser extensions are available.
Tresorit Send lets you freely share files with end-to-end encryption via a link that you can send to anyone that automatically expires after 7 days or after 10 downloads.  If you provide your email address, the link can be password protected and revoked and link access can be tracked.  No signup or download required for files up to 5 GB.  Browser extensions are available.
Send Secure Message
ProtonMail allows you to send end-to-end encrypted emails to anyone.    Messages sent to recipients without a ProtonMail account will require setting a password and will automatically expire in 1 hour to 28 days.  The sender must create an account (free or paid).  No download is required.
Gmail Confidential Mode allows you to send emails that expire in 1 day to 5 years or that may be revoked.  Recipients are restricted from forwarding, copying, printing, and downloading confidential emails.  The sender can require a passcode to access email content.  Gmail Confidential Mode does not provide complete end-to-end encryption -- Google has access to email content.  A Gmail account is required.
Signal allows you to send and receive end-to-end encrypted group, text, voice, video, document, and picture messages to other Signal users.  Phone and desktop apps are available.  Download is required.
Sendinc allows you to send end-to-end encrypted emails to anyone.  The emails expire in 7 days.  The sender is required to create an account (free or paid).  No download is required.

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