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Custom patched DavMail installation instructions

The patch

The given patch davmail-userwhitelist.patch adds the davmail.allowedUsers option to the configuration which accepts a comma-separated list of emails to allow into the server. This protects (somewhat) from other users who might find your DavMail instance (or are otherwise on the same shared Exchange instance [such as MS hosted exchange]).


You can either manually patch Davmail's sources using the provided patch, or use Docker to build a .deb for you. This will always build the latest version of Davmail from the Debian repositories (ensuring it is suitably packaged with init scripts and the like, unlike the .deb that comes from the developer).

  1. Ensure Docker and Docker Compose are installed.

  2. Run the following:

    git clone
    cd djb.davmail
    docker-compose up
  3. Enjoy your new package, available in the build/ directory.

If you're not into Docker, then you can use the script directly on your own Debian VM. You'll need to ensure you have set up the basic dependencies of building debs first; see the Dockerfile file for more information.

Installation on server

  1. Copy package produced above to server. Install it with:

    sudo apt update && sudo apt install -y gdebi0-core
    sudo gdebi ./davmail_*.deb
  2. Edit /etc/ to configure your Davmail instance

  3. Add security certificates into the appropriate .p12 keystore

  4. Configure the OS accordingly to permit Davmail to listen on privileged ports, either:

    1. Run it as root (not recommended), or

    2. Enable capabilities:

      sudo apt install -y libcap2-bin
      sudo setcap 'cap_net_bind_service=+ep' $(readlink -f $(which java))
  5. Unmask the service:

    sudo systemctl unmask davmail
  6. Control Davmail with:

    sudo systemctl {start,stop,restart,status} davmail

You can reinstall a new package straight over the top when required.


  • Use to locate EwsUrl details for inclusion into this configuration file. On this page, click Outlook Autodiscover and follow the steps. On the successful test results page, keep expanding nested test results (there are lots of them!) until you get to a POST result with a variety of XML details. There should be a <EwsUrl> tag included -- use this URL.

  • Note that the init.d script doesn't log output from the server (save on IO cycles).

  • The .private file may contain private information like the davmail.allowedUsers option and email addresses, and also davmail.ssl.keyPass and davmail.ssl.keystorePass passwords. It should look like this:

    davmail.allowedUsers =,
    davmail.ssl.keyPass = password
    davmail.ssl.keystorePass = password
  • Beware of trailing spaces or other characters at the end of the password lines above. If you have any whitespace afterwards, you will tear your hair out trying to solve this error:

    Exception creating secured server socket : failed to decrypt safe contents entry: javax.crypto.BadPaddingException: Given final block not properly padded
  • Convert an official SSL certificate from a CA into P12 format using the following:

    openssl pkcs12 -export -in -inkey -certfile ca_bundle.crt -out davmail.p12

    The Export Password you specify will be that which you need to use as the keyPass and keystorePass options above.

  • Generate a self-signed davmail.p12 keyfile using the following:

    keytool -genkey -keyalg rsa -keysize 2048 -storepass password -keystore davmail.p12 -storetype pkcs12 -validity 3650 -dname,ou=davmail,o=sf,o=net

    Note that keytool sets both the keypass and the storepass to the same value once just storepass has been configured. Weren't you glad you asked?


DavMail patched build using Docker.




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