There are many aspects that govern the performance of an organization. One of the most important thing is their organizational structure. Having a well-planned organizational structure facilitates good internal communication among the employees, which in turn contributes to the success of the organization. Today, company re-structuring is very common in the industry. When various key employees are re-organized (moved to different hierarchical positions), the company might experience certain incidents which can be damaging or beneficial for the company. To leverage the potential gain, having an efficient organizational structure is very important for a company. The primary objective of this study is to analyze the existing organizational structure of the company by the evaluation of email communications between the employees, and if required suggest the need for re-organization. In this case study, we have applied various cluster validation techniques to evaluate the email communications between the employees. The data (email logs) are provided by the company which have been recorded at different time periods. We have analyzed the organizational structure through the analysis of these email logs. We have then simulated various re-organization scenarios. By applying various cluster validation metrics, we have examined the quality of the existing organizational structure. We have also recorded how re-organization (moving employees from one organizational unit to other) effects the overall quality of the existing organizational structure of the company. In this study, we have presented how different cluster validation metrics will be helpful in assessing the quality of the organizational structure by reflecting the different aspects of the organizational structure. We have shown that our approach makes it possible to evaluate the effects of different re-organization scenarios on the internal communication patterns of employees in an organization. All these metrics can be used by the company to improve their existing organizational structure.