Figure 4.5 shows offline email system
network protocol layout. When email is sent, a message was sent from the sender
mail server Mail Transport Agent (MTA). Both MTA side communicates using Simple
Mail Transfer Protocol (SMTP) Server. The recipient MTA delivers the email to
the Mail Delivery Agent (MDA) which stores the email as it wait for the user to
accept it. Internet Message Access Protocol (IMAP) used for retrieving email on
MDA.
Figure 4.5:
Offline Email System Network Protocol layout
MDA is protected by login system
where it needs a username and password. Email is retrieved by using Mail User
Agent (MUA) where it is called an email client on the user device. Webmail is
used for this thesis work. If the email destination is not in the local
network, the email delivery is pending and the data remain in the mail server
storage until it is transferred to the infomediary device. This operation
matches the bundle protocol (BP) where the data being stored temporarily and
later forwarded to next destination. When the infomediary device establishes a
network connection with the offline mail server, the mail database synchronization
application will transfer the email data from offline mail server to infomediary
device and retrieve new email data from infomediary device to the offline mail
server. The new email data from infomediary device which is received from online
mail server will be in the new pending email delivery where it is being sent
immediately since the destination was in the network until it reaches the user
to accept it. The Dynamic Host Configuration Protocol (DHCP) is a network
protocol used to configure devices that are connected to a network. The SSID
and security codes for the access points are chosen by the administrators. This
offline email system used static IP addresses. Both the online and offline server
computers are configured as DHCP servers. This enables the servers to allocate
IP addresses to any DHCP client.
Figure 4.6 shows online email system
network protocol layout. The process is the same as when the infomediary device
establishes a network connection with online mail server, the mail database synchronization
application will retrieve email data from infomediary device to online mail
server and transfer the new email data from online mail server to the infomediary
device to be sent to the offline mail server. The email data from infomediary device
which is received from the offline mail server will be in pending delivery
where the delivery is executed immediately because of the destination is
available in the network until it reaches the user to accept it.
Figure 4.6:
Online Email System Network Protocol layout
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