MailCrypt

The software has builtin support for Dovecot’s mailbox encryption, using the global keys mode. Keys are created and maintained by userli and handed over to Dovecot via checkpassword script.

The MailCrypt feature is enabled per default and can optionally be switched off globally by setting MAIL_CRYPT_ENABLE=0 in the dotenv (.env) file.

If you want to enable MailCrypt for some users, but don’t want new users to have MailCrypt enabled per default, you can set MAIL_CRYPT_AUTO=0 in the dotenv (.env) file.

In order to enable MailCrypt in Dovecot, the following is required:

  • Add mail_crypt to the mail_plugins list in /etc/dovecot/conf.d/10-mail.conf
  • Set mail_crypt_save_version = 0 in /etc/dovecot/conf.d/90-mail-crypt.conf

The latter disables MailCrypt per default and is necessary to not break incoming mail for legacy users without MailCrypt keys. The checkpassword script automatically sets mail_crypt_save_version = 2 for all users with MailCrypt keys.

MailCrypt can be turned on/off for individual users by setting the mailCrypt switch in the virtual_users database table. This switch is mainly meant to provide a migration path from legacy users without MailCrypt keys. On new setups, it’s recommended to keep MailCrypt enabled for all users.

    Migrating legacy users

    Legacy users (without MailCrypt keys) continue to work without mailbox encryption. If they generate a recovery token manually in the account settings, a MailCrypt key pair gets created for them. This doesn’t enable MailCrypt for them automatically, though.

    Implementation details

    Cryptographic primitives