A third-party, open-source ProtonMail bridge. Hydroxide supports CardDAV, IMAP, and SMTP protocols. Key Features: No GUI, only CLI Standards-compliant (not optimized for Microsoft Outlook) Fully open-source What is Hydroxide? Hydroxide is a server that translates standard protocols (SMTP, IMAP, CardDAV) into ProtonMail API requests. It allows you to use your favorite email clients (like Apple Mail or Thunderbird) or tools like git-send-email with ProtonMail. Commands: auth username Login to ProtonMail via hydroxide carddav Run hydroxide as a CardDAV server export-secret-keys username Export secret keys imap Run hydroxide as an IMAP server import-messages username [file] Import messages export-messages [options...] username Export messages sendmail username -- args... sendmail(1) interface serve Run all servers smtp Run hydroxide as an SMTP server status View hydroxide status Global options: -debug Enable debug logs -api-endpoint url ProtonMail API endpoint -app-version version ProtonMail application version -smtp-host example.com Allowed SMTP email hostname on which hydroxide listens, defaults to 127.0.0.1 -imap-host example.com Allowed IMAP email hostname on which hydroxide listens, defaults to 127.0.0.1 -carddav-host example.com Allowed SMTP email hostname on which hydroxide listens, defaults to 127.0.0.1 -smtp-port example.com SMTP port on which hydroxide listens, defaults to 1025 -imap-port example.com IMAP port on which hydroxide listens, defaults to 1143 -carddav-port example.com CardDAV port on which hydroxide listens, defaults to 8080 -disable-imap Disable IMAP for hydroxide serve -disable-smtp Disable SMTP for hydroxide serve -disable-carddav Disable CardDAV for hydroxide serve -tls-cert /path/to/cert.pem Path to the certificate to use for incoming connections (Optional) -tls-key /path/to/key.pem Path to the certificate key to use for incoming connections (Optional) -tls-client-ca /path/to/ca.pem If set, clients must provide a certificate signed by the given CA (Optional)

1. Authentication

Before running the container, you must authenticate with your ProtonMail account. You have two options:

    Run this command:

    docker run -it --rm -v /mnt/user/appdata/hydroxide:/root/.config/hydroxide docker.io/heywoodlh/hydroxide auth user

    Replace user with your ProtonMail username or email address.
    Alternatively, if you already have a Bridge Password, set it using the HYDROXIDE_BRIDGE_PASS environment variable.

2. Host Configuration

    Ensure the listening hosts (-imap-host, -smtp-host, and -carddav-host) are correctly set to match your desired hostname in the post arguments.

    If you don’t wish to use a custom network, set the network type to bridge. For this to work, port 8080 (used for CardDAV) must be available.

    If port 8080 is already in use (e.g., by Nginx Proxy Manager), you can also disable CardDAV entirely by adding -disable-carddav to the post arguments.