Email system was first developed for ARPANET in 1970. Then later on, it became the widely used messaging service on internet. It faced many milestones in the earlier stage for implementation like timesharing computer, read-mail, send-mail, RD, NRD etc. But with time, these milestones were overcome with new technologies. Now emails are been used in every sector of life. It is used in industries, companies, organization, schools and colleges etc. The main techniques involved in email are POP3, IMAP, MAPI, SMTP etc. These are the main protocols used in providing various services of emails. Emails can be clustered to make it more efficient for retrieval of mails.