It is important not to ignore a cease and desist letter. In sending a cease and desist letter, the sender has already indicated a willingness to take the addressee to court.
If the letter contains a deadline, recipients should bear this date in mind and make sure that any investigations conducted by the recipient into the allegedly illegal action will be finished in time to allow for a reply to the letter to be sent.
An investigation will help the recipient decide whether the reply to the letter will comply with the cease and desist or will reply to the sender denying (with evidence) any wrongdoing.