A federal judge ordered the White House to preserve copies of all its e-mail messages, a move that Bush administration lawyers had argued strongly against. The order, from Judge Henry H. Kennedy Jr. of Federal District Court, came in response to two lawsuits trying to determine whether the White House destroyed e-mail messages in violation of federal law. Two private groups that filed suit, Citizens for Responsibility and Ethics in Washington and the National Security Archive, say 5 million messages have disappeared. Judge Kennedy’s order is directed at maintaining backup tapes that contain copies of messages.