Mailfence

Mailfence is an encrypted email service that offers OpenPGP based end-to-end encryption and digital signatures. It was launched in November 2013 by ContactOffice Group, which has been operating an online collaboration suite for universities and other organizations since 1999.
History.
Development.
In the midst of 2013, the Mailfence project was started by the founders of ContactOffice. In March 2016, a beta version of end-to-end encryption and digital signatures for emails was released.
In January 2021, Mailfence released progressive web application for mobile devices.
Block in Russia.
On 05 March 2020, Mailfence reported that their SMTP servers are blocked by Russian based email services. This was in response to their refusal to submit a Notice of Commencement of Collaboration with Roskomnadzor’s (the Federal Supervision Agency for Communications, Information Technology, and Mass Communication) of the Russian government. Mailfence did not respond to this request, citing obligation to provide information about users, violating its Terms and the federal Belgian laws. 
Features.
Mailfence provides secure email features, with other functions such as Calendar, Contacts, Documents and Collaboration.
Encryption and Two-factor authentication are available in the free version of the product. Most other features are only available with paid subscriptions that start at 2,50 € per month.
Email.
The service supports POP/IMAP and Exchange ActiveSync as well as vanity domains with SPF, DKIM, DMARC and catch-all address support. Users can send both plain and rich text emails, organize messages in folders and/or categorize them with tags, take notes by setting comment on each message and create default message signatures for every sender address. Different identities can also be managed using aliases and filters for incoming emails. 
Contacts.
The contacts support (CSV, vCard, LDIF) import, (vCard, PDF) export and can be accessed using CardDAV. Users organize them with tags and can also create contact lists.
Calendar.
The calendar supports vCal/iCal import, export and can be accessed by using CalDAV. Users can share their calendars with group members and can also create polls.
Documents.
The documents can be accessed using WebDAV or edited online. Users can drag and drop files in folders, categorize them with tags take notes by setting comment on each file.
Groups.
Groups allow users to share mailboxes, documents, contacts, calendars and perform instant chatting with group members in a secure way. A group administrator manages the access rights of group members and can also set another group member as co-admin or the main admin of the group.
Web-based clients.
The web-interface comes with an embedded IMAP, POP3, CalDAV, and WebDAV client. Users can add external accounts and manage them centrally in the web-interface.
User management.
Account owners can create and manage user accounts using the admin console.
Server location.
Since their servers are located in Belgium, they are legally outside of US jurisdiction. Mailfence is therefore not subjected to US gag orders and NSLs, notwithstanding extradition treaties with the US. Under Belgian law, all national and international surveillance requests must go through a Belgian court.
Security and privacy.
Aside from conventional security and privacy features including managing access or generating specific password for web and non-web services, two-factor authentication, spam protection alongside of plus addressing, sender address blacklist and whitelist, Mailfence offers following features:
Transport security.
The service supports HTTPS and uses TLS with ephemeral key exchange to encrypt all internet traffic between users and Mailfence servers. Their 4096-bit RSA SSL certificate is signed by Buypass AS and supports Certificate Transparency and Strict Transport Security. Mailfence.com holds an "A+" rating from Qualys SSL Labs and also supports DANE. 
End-to-end encryption.
The service uses an open-source implementation of OpenPGP (RFC 4880) for emails. OpenPGP keypair is generated in client-browser, encrypted (via AES256) with the user's passphrase, and then stored on Mailfence server. The server never sees the user's OpenPGP keypair passphrase.
The service also supports end-to-end encryption for emails using a shared password with the possibility of message expiration.
OpenPGP signatures.
The service gives the choice between "signing", or "signing and encrypting" an email message with or without attachments.
Integrated Keystore.
The service provides an integrated keystore to manage OpenPGP keys, and does not require any third-party add-on/plugin. OpenPGP keypairs can be generated, imported or exported. Public keys of other users can be imported through file or in-line text or can be downloaded directly from Public key servers.
Full OpenPGP interoperability.
Users can communicate with any OpenPGP compatible service provider.
Warrant canary and transparency report.
The service maintains an up-to-date transparency report and warrant canary.