Posteo does not store any personally identifiable information, thus guaranteeing the user's complete privacy and shielding the user from surveillance by the authorities.
Also based in Germany, Posteo is a bit different from Tutanota and ProtonMail in that it's a secure email service that encrypts server connections using TLS (using DANE and full forward secrecy) and stores all emails on an AES-encrypted hard drive (key size unknown). By default, Posteo is not an e2e encryption service, however, through ‘one-click’ OpenPGP and S/MIME support in the browser, Posteo supports end-to-end email encryption, where the recipient's computer must have the same type of encryption software installed (OpenPGP or S/MIME whichever the user prefers), but does not have to be a Posteo user.
Posteo also runs its own PGP key directory, which is more private than traditional PGP key servers, and the Roundcube web interface works well in mobile browsers, but Posteo does not have a dedicated mobile APP, but Posteo does support IMAP, which means that third-party email apps can be used with the service. in 2013, the service successfully resisted a police request for the identity of Posteo account holders, demonstrating its ability to protect privacy, and as the service does not store any data on customer identity, it is not possible to provide such information.
