If the idea of the project is about emails classification. So you can write the project idea as follow:
Text Classification is the process of assigning tags or categories to text based on content. There are many applications for text classification, such as question type classification, topic labeling, sentiment analysis, and spam detection. Spam detection is the one important application of the Natural Language Processing field. The aim of this project to build a mobile application that classifies Arabic emails to spam or not spam.