* comment: The prefix of subject to show test environment or not
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getMailSubjectTestPrefix();

    /**
     * Get the value for the key 'mail.return.path'. <br>
     * The value is, e.g. root@localhost <br>
     * comment: The common return path of all mail