Makes me wonder if its possible or reasonable to consider an option with protonmails (and similar) - have a note in the footer of the email - explaining that encrypted is default in their system, but sending to your email provider has it converted to plain text where others can access it.. if you'd like to keep this mail message private click to login to protonReadPortal - where you can read, and if you'd like make a passphrase, to reply and keep messaging on secure servers.. get an optional app for replies to your contacts that have proton accounts.. then tap to checkbox so further emails to you from proton accounts send you a notice to check out the protonReadPortal instead of including the plain text..

I'd want my protonReaderApp to have default shred message after reading.. keep available on proton server for 48 hours after.. one click to save as pdf or zip or other safer password format, or save on protonServer longer.. with easy to change defaults..

would be nice option. I dunno maybe something like this exists?

There are several use cases for this..

a system like this could make for encrypted form storage and messaging with the right API maybe hippa compliant?

I'd expect my lawyers and accountants and such to use something like this.