According to the Customer Care page provided by the Rediff, an email account is created for life. There is no manual way to delete it. They say that if you don't access the email account for 90 days, the system will automatically delete it. After 60 days, all the email in that account is deleted then it's marked for deletion if no one will visit it for the next 30 days. To read more, access the support page provided above.
