Are there any free software or open source based anonymous or encrypted web-mail services out there?
 

Hi,
I'm wanting to find a web-based e-mail service that is free software based (preferably on a GNU General Public License) or, barring that, I'd begrudgingly settle for an open source based web-mail service.
Even better still, I'd like to find one that has truly anonymous and encrypted email features at its core. All without downloading and installing a new e-mail client to my operating system and just strictly running web-mail through my browser window only. Does anyone know of any that I can create an account on or sign for to start using such a web-based e-mail service?
Thanks

Another option is to use a mail client (like Claws, KMail, Evolution, Mutt or Thunderbird) with a GnuPG plugin. Both you and the person you're communicating with would need to set that up.

Other than that? The only thing I can think of is ProtonMail, which isn't really what you described.