Electronic Mail

Electronic Mail (Email) is a method of exchanging digital messages over the internet that allows users to send and receive messages, which can include text, attachments (such as documents or images), and multimedia content.

• Email has become one of the most widely used forms of communication, both personally and professionally.

• Emails are sent through email servers using protocols, ensuring that messages are delivered to the correct recipients and properly stored until they are retrieved by the recipient’s email client (like Outlook, Gmail, etc.).

Working of Email

The working of email involves several key steps that include both client-side (user) and server-side (mail server) actions.

Here’s how email works:

Composing an Email:

• The user composes a message in an email client (such as Gmail, Yahoo Mail, or Outlook).
• The email contains the recipient’s email address, subject, body, and any attachments.

Sending the Email:

• The email client sends the composed message to an outgoing mail server (usually using the SMTP protocol).

Message Routing:

• The email server communicates with the DNS (Domain Name System) to find the mail server address of the recipient.
• Once the recipient’s mail server is found, the email is transferred to that server.

Receiving the Email:

• The recipient’s mail server stores the email.
• The recipient accesses the email by using an email client or webmail, which retrieves the message from the server using protocols like IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol).

Reading the Email:

• The recipient reads the email, and the email client downloads and displays the message along with any attachments.

SMTP (Simple Mail Transfer Protocol) Packet

SMTP (Simple Mail Transfer Protocol) is the protocol used for sending and relaying outgoing email messages between email clients and servers.

• SMTP ensures that email messages are correctly routed and delivered from the sender to the recipient.

• When an email is sent, an SMTP packet is generated. This packet contains all the necessary information for the mail server to send and deliver the message.

An SMTP packet includes:

Mail Header:

• Information about the sender, recipient, subject, and other metadata.
• Example: From: sender@example.com, To: recipient@example.com

Mail Body:

• The content of the email, which can include plain text or HTML-formatted text.

Attachments (Optional):

• Files that are sent with the email (images, documents, etc.), which are encoded into the packet.

Control Information:

• The protocol used to send the email and how the mail server should respond (e.g., confirmation of receipt or delivery failure).

Multipurpose Internet Mail Extensions (MIME)

Multipurpose Internet Mail Extensions (MIME) is an extension to the original email protocol (SMTP) that allows for the transmission of multimedia content, including images, audio, video, and other file types. MIME enables email to support content types beyond just plain text.

When sending an email with MIME:

• Encoding: MIME allows for the encoding of non-text content (such as images and audio) into a text format that can be safely sent over email. For example, binary files like images are converted into base64 encoding.

• Content-Type: The MIME standard introduces a Content-Type header, which specifies the format of the content being sent, such as:
  • Content-Type: text/plain for plain text emails.
  • Content-Type: text/html for HTML-formatted emails.
  • Content-Type: image/jpeg for image attachments.

• Attachments: MIME allows email messages to include multiple parts, such as text in the body and various attachments (like documents, spreadsheets, images, etc.).

• Multipart Messages: MIME also supports multipart messages, which can contain different parts with different content types. For example, an email might have a plain text version and an HTML version of the same message to cater to different email clients.