Cloud Computing is the next generation technology that describes the development of many existing technologies and approaches to computing into something different. Cloud enhances agility, scaling, and availability, and provides the potential for cost reduction through optimized and efficient computing[1]. Cloud Computing has the potential to change the nature of Information and Communication Technology (ICT) provision in the public service and significantly reduce costs[1]. It is a key element of strategic future of ICT in this sector. Cloud Computing services are delivered by any third party provider who has its own infrastructure. As cloud is a collection of super computers which are spread all over the world, hence authorization and authentication are extremely necessary. This paper proposes a methodology to over come the security threats that can take place on three levels i. e login authentication, network security and Storage Security. We have built an Email system to provide security on all three levels. Firstly, user authentication is done so that an unauthorized user cannot tamper the data of authorized user. Secondly, when the user wants to check its inbox, then he is supposed to enter the passcode i. e Storage Security via RC4 is done. Thirdly, while sending a mail to someone through network is done with the help of AES (Advanced Encryption Standard). Hence, the integrity and confidentiality of data saved in inbox or mailed to another user is ensured by not only encrypting but also providing access to data only on successful authentication.

AES(Advanced Encryption Standard) RC4.