I've just signed up for this. It looks like exactly what we want from 'secure' email: (0) you can send unencrypted email just like any other webmail service.

I've just signed up for this. It looks like exactly what we want from 'secure' email: (0) you can send unencrypted email just like any other webmail service. PLUS (1) end-to-end encrypted if sender&receiver use tutanova. (2) if receiver does not use tutanova, you can still send them encrypted email if you want to: they get an email saying - 'you have an encrypted mail, click this link to view it' - on clicking the link, they decrypt the mail by entering a pre-agreed password. (3) it is free. they seem to be making money from the 'enhanced features' in their 'Outlook Addin' package.