Due to the increasing usage of email for communications and other tasks, effective email management is becoming more and more important. People put a lot of efforts into organizing, storing, and searching to efficiently manage and maintain the useful information in their emails. There are several kinds of email systems that people use extensively, which are "folder-based" (Microsoft Outlook Express), "search-based" (Yahoo! Bloomba), "category-based" (Apple Mail), and so on. This thesis will analyze these systems and also present a novel method to effectively and efficiently organize, manage, maintain, and search emails based on database technologies. We call the new system a "multi-dimensional categorization hierarchy-based" email management system, because it manages emails by using various categories, instead of the directories or folders used in traditional email systems. As opposed to folder-based or category-based systems, our email system allows an email to be classified into more than one category, while a category can also have multiple parent categories in the same dimension. These features give users the flexibility to organize their emails within various categories and to make email management more effective than ever before.