The domain name which comes after the symbol@, may also include an extension other than .com which stands for commercial business. It may be on educational institution ‘edu’, on organisation ‘org’ or government departments ‘gov’. Domains are classified as non geographics and geographic, countires have fixed domain names: eg. the domain name of the UK is .uk and that of India is .in. There may be sub domains that correspond to organisations such as NASA.