False Allegations Using Gmail Id

My friend and her husband recently got married and my friend comes to know the Sadistic behavior of her husband after marriage. So, both sides decided to opt for mutual divorce. My friend is working in a nationalised bank and due to the grudge on her, her husband sent email to the higher officials stating all false allegations and tried to defame her in the email using unparliamentary language. Later, my friend comes to know that the email was sent by her husband using fake Gmail id. He don't even have any bank account in the branch where she is working. He is not a customer of that bank. Now, she wants to file a case in police station. If she files a complaint, can that person gets any punishment? What sections she should put while filing a case? Please let me know. Thanks.