Employee claiming Dues without Handover

We have few employees who have emailed resignation without a handover and now claiming their dues in spite of the company telling them that please do a proper handover and take your dues. Their Resignation have also not been accepted. They have been emailing repeatedly saying we have handed over, please clear dues. Company needs the handover to be done completely which is not done by them but they are mentioning that they have done it in their emails. There are no signed copies of the Handover from both the sides Is the employer still liable to pay the dues without handover which he is not ready to do. What can be the challenges from the employer's point of view and how can he resolve the same?