code: public ApiResponse<Void> postUiOpenwindowNewmailWithHttpInfo(String datasource, String token, UiNewMail uiNewMail)
              throws ApiException {
          com.squareup.okhttp.Call call = postUiOpenwindowNewmailValidateBeforeCall(datasource, token, uiNewMail, null);
          return apiClient.execute(call);
      }
docs: Open New Mail Window Open the New Mail window, according to settings from
  the request if applicable --- SSO Scope: esi-ui.open_window.v1
  
  @param datasource
  The server name you would like data from (optional, default to
  tranquility)
  @param token
  Access token to use if unable to set a header (optional)
  @param uiNewMail
  (optional)
  @return ApiResponse&lt;Void&gt;
  @throws ApiException
  If fail to call the API, e.g. server error or cannot
  deserialize the response body