While there are some lies for which you can be prosecuted--for example, a false police report, false tax return, etc.--generally, a false internal company email would not result in prosecution as wrong as it is, it is not a crime. However, you wife could clearly be fired "for cause" so no unemployment could be sued by the company if, in reliance on her email, they did anything costing them money and could be sued by the other employees for defamation, if they suffered any negative effects or consequences.