The functionalities that are performed from backend as follows:

The server usage the message storage DIRECTORIES and the directory user agent to keep track of all the clients that are in sync with the server or communicating with it. 

• Directory services are provided to manage the names of the clients, their email ADDRESSES and the distribution lists so that they can be reached in case of any loss of information. 
• Message Transfer Agents (MTA) delivers the email to the recipients who are residing somewhere else from time to time and allow them to answer them back. 
• Email APPLICATION Programming Interface (API) allows easy INTEGRATION of the subroutines and function that enable the program to access various components like MAPI, VIM, etc to be USED with the email system. 

The use some predefined protocols to establish the communication between the two computers or two servers defined at a location.

The functionalities that are performed from backend as follows:

The server usage the message storage directories and the directory user agent to keep track of all the clients that are in sync with the server or communicating with it. 

The use some predefined protocols to establish the communication between the two computers or two servers defined at a location.