Architecture and Services of E-mail | Computer Networking
How does E-mail System work?

Architecture and Services of E-mail | Computer Networking

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In this post, we are going to study about very important and curious topic that is – Architecture and Services of Electronic Mail and we will also know about how does the Email system works? and what is the mechanism to be used in the E-mail system?. we have studied about Overview of E-mail in the previous post. So now, this time is to know about how does email system works?

Architecture and Services of E-mail

As we know, Email Systems are being used on a large scale in daily life. Most of the Business Industry’s employers use Email systems to send and receive sensitive or non-sensitive information on their systems. But should we need to know about How does the Email system work and what is the architecture, and which type of services are provided by the E-mail?

>>I think you should know about this to become bit more technical.

Let’s start our journey to become bit more technical.

E-mail System consists of two sub-systems

Especially, Email System mainly contains two major sub-systemsuser agent(Google Gmail) and message transfer agent(SMTP).

1: User agent – (Brief Overview)

This sub-system(user agent) does work upon the application interface. This interface may be either Graphical Interface or text-based Command interface, which allow people to read and send email to the other members. User Agent sub-system is also known as email readers.

2: Message transfer agent – (Brief overview)

This sub-system(message transfer agent) does work on virtual network layers(mainly Transport Layer). This sub-system allows the user to move the message packets(user’s email) from one source to the intended destination. In other words, this sub-system mainly works onto message transfer from sender to receiver and vice versa.

Note: Message transfer agent sub-system is also known as mail servers.

What is SMTP(Simple Mail Transfer Protocol)?

SMTP stands for Simple Mail Transfer Protocol. This protocol is used to send every single mail to the intended recipient. In other words, SMTP is a rule that must be followed by every single mail system service.

SMTP was originally specified as RFC 821 and revised to become the current RFC 5321. It sends mail over connections and report back the delivery status and any errors. Numerous Application exist in which confirmation of delivery is important and may even have legal significance.

User Agent – Full Explanation

Generally, User Agent is a program that provides a graphical or command based interface that lets users interact with the email system. User agent provides you to the ability to compose message and their replies, display incoming messages, and organize message by filling, searching, and discarding them. The act of sending new messages into the mail system for delivery is called mail submission.

The User-Agent sub-system does automatically filtered incoming mail packets according to its type, such as social, updates, primary, promotions, spams e.t.c. These are the different types of mail messages coming from different sources.

Some advance User-Agent provides an advanced facility for us to send automatic reply responses to all mail senders. If we say in other words, Advance User-Agent generates automatically reply responses according to mail sender’s message without any user interaction. This feature is helpful for those peoples who want to give specific replies to all the senders.

There are many popular user-agents, including Google Gmail, Microsoft Outlook, Mozilla Thunderbird, and Apple Mail.

Message Transfer Agents: Full Explanation

Message Transfer Agents are system processes. They run in the background on the mail server machine and are intended to be always available. Their job is to automatically move email through the system from the originator to the recipient with SMTP. This is the message transfer step.

Message Transfer Agents also provides us a mailing list, in which an identical copy of the message is delivered to everyone on a list of email addresses.

Advance features are carbon copies(cc), blind carbon copies(bcc), high-priority email, secret(encrypted) email, alternative recipient if the primary one is not currently available, and the ability for assistants to read and answer their bosses’ email.

Linking user agents and message transfer agents are the concept of mailboxes and a standard format for email messages. Mailboxes store the email that is received for a user.

Mail is sent between message transfer agents in a standard format. The original format, RFC 822, has been revised to the current RFC 5322 and extended with support for multimedia content and international text format. This scheme is called MIME(Multipurpose Internet Mail Extensions).


Conclusion – These sub-systems are the basic or fundamental parts of the Email System. User Agent and Message transfer Agent both are the building blocks of E-mail System.


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Prajjwal Singh

Tech Blogger || Web developer || Computer Networking Enthusiast || Microsoft SQL Database Management Expert || Software Debugger || Learned DOS OS Structure

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