If anyone can find any other established provider that have all our privacy and security features, we will give that person $10k as a reward! --Simon Persson Founder Countermail
Security at countermail is the best anywhere
My initial concern was about how they use Java. Java has this reputation (deserved or not) of being a security risk. They explain this very well why they use Java for email encryption. This only affects webmail, if you're using IMAP with a client like Thunderbird it's not a concern.
If you don't want to install Java in your everyday firefox browser there are a few solutions.
The webmail interface only support inline PGP, but there are buttons to View / Download so it's an extra click to see a PGP/MIME encrypted email. Using a client like Thunderbird and Enigmail, there's no difference.
Countermail has a few things no one else does on their Tools page encrypt, decrypt, verify, analyze SSL cert, PGP packet analyzer, plus a few more pgp tools.
Contacts and the calendar are encrypted. Key management is integrated with the Contacts app. Calendar is also kept encrypted with plan to support CalDev calendar syncing in the future.
Countermail encrypts your email with your public key. Unlike Startmail who uses their own key to encrypt incoming mail. That means ALL of your incoming email is encrypted with your public key when it arrives and is stored on disk. This is completely transparent and doesn't affect forwarding or replying to unencrypted emails. All keys generated by Countermail are 4096 bit.
Sweden is still in the 14 Eyes Spy Cartel but does it matter with all of the security and zero knowledge in place?
Countermail is a little more complicated than others, especially since firefox doesn't enable Java as a default and some of the interface options may not be obvious. Support people are awesome and quick, the knowledgebase is very well done.Worth the extra effort.