1.2  Problem Statement

TCP/IP does not fully support this offline email system because it requires immediate end-to-end path between sender and receiver. This means the connection must exist at the same time sender send the email because the email packets will travel through the transport layer and finally to the destination. The email client is disconnected from email server if there is no end-to-end path and the user cannot access their email account. However, if the Gmail offline application is used, the user has to bring their device to the connected area. In rural area, this seems not practical. Delay tolerant network (DTN) is designed to overcome this limitation by implementing store and forward message switching by overlaying a new protocol layer called the bundle layer. DTN use storage within the network to support the store and forward operation over networking paths. The problem arises when the emails have to be collected into another device before it is brought physically to the connected area. The store and forward process of DTN is integrated using the file synchronization method because it involves the third device and the third person to bring the emails to the connected area.