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  1. The best and most secure solution is to buy a YubiKey directly from us. This special YubiKey will authenticate your identity by connecting to a dedicated YubiKey server in our data center. No data is transfered to third parties.
    In general, hardware tokens offer better security than software solutions on a mobile phone. See the FAQ article about YubiKeys for further details.
  2. Alternatively, you can use a generic Yubikey bought from Yubico. This key will perform authentication using the world-wide YubiCloud service.
  3. With a hardware token: you can use HOTP or TOTP compatible tokens like "Nitrokey Pro or Nitrokey Storage" for the login to our web interface.
  4. As a third variant, users may opt for any OATH-, TOTP-, HOTP- oder mOTP-compatible token generator such as those employed by smartphone apps like FreeOTP, Google Authenticator, or OATH Token.

We do not offer SMS based 2FA and this ist not planned for the future.

The 2 factor authentication is only available for our web interface. The other services like IMAP, POP3, SMTP and also WebDAV, CalDAV and CardDAV do not support 2FA.
Please ensure to allow the needed cookies in your web browser.

Important: If you loose your Yubikey or your token, you can only reset your password (and switch off 2FA), if you provided some information for the password reset procedure. Otherwise, we cannot help. login with PIN and One-Time-Password

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If you want to login with PIN and OTP password in our office webinterface, you have to enter the 4-digit PIN and the One-Time-Password for password input without any whitespace char.

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If you use two-factor authentication, the following restrictions apply:

  • You cannot change your main e-mail address as long as you have selected one of the two OTP options under "Settings -> -> One Time Passwords -> OTP backup level".
    If you want to change the main e-mail address, you must first change the option "OTP security level" to "Off, use normal passwords only". Then you can change the main e-mail address and log back in with it. Finally, reset your OTP security level as desired. We are working on a bugfix.
  • You cannot log in to the office with several browsers or devices at the same time using a web client.
  • By using two-factor authentication, you can only log on once at a time.
  • You must log out before closing the browser.
    Although it should be common practice to log off before closing the browser, it is absolutely necessary when using one-time passwords! Otherwise you will receive an error message the next time you log in.
  • If you set the OTP backup level to "OTP only for web interface, all other services off", logging into our helpdesk and the user forum is no longer possible!

Configuration of PIN and OTP password

In the Office , go to Settings → you can select the desired authentication method under "Settings -> -> One Time Passwords to select your preferred authentication method.

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Set a 4-digit PIN and select the desired OTP security level and method. 

-> OTP Method":
Specify the four-digit PIN and the desired security level. Then select the desired method to generate one-time passwords: via or with one of the other methods.

We offer two different levels of two-factor authentication:

  1. Webinterface OTP, everything else password: With this option you set up so that it works like most other e-mail providers with two-factor authentication. You can log in to the web interface with your PIN and one-time password and continue to use all other services such as IMAP, POP3, SMTP, WebDAV, CalDAV, CardDAV or ActiveSync with your (normal) password. So you can continue to use local email clients on your PC or smartphone, synchronize calendars, etc.
  2. OTP only for web interface, all other services off: This is a special feature of If you select this option, you can only log in to the web client, the office with secret code and one-time password. All other services will be deactivated for your account. You will not be able to use local email clients or synchronize data.

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Don't forget to click on "Submit".


After having created an OTP token for a smartphone app, just scan the QR code with your phone to set up the app for generating valid tokens.

Lost token - what now?

If you have lost your token, you can still use the function to reset your password. The moment you reset your password e.g. by e-mail or a reset code via SMS, you can create a new password. This also deactivates two-factor authentication. With this new, regular password you can log in again - and have access to all functions of your office as usual.

As already mentioned above, you can only reset your password if you have stored the corresponding information in your account. If, for example, you have not entered an e-mail address or a mobile phone number for a password reset for reasons of anonymity and access to your e-mail account via IMAP is deactivated, then we have no way of verifying your identity as the owner of the account.
In this case a password reset is no longer possible!

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If you use two-factor authentication, the following restrictions apply