Email & Its Protocols

What is Email?

Email (Electronic Mail) is the method of sending and receiving digital messages over the internet. It is one of the oldest internet services, predating the World Wide Web itself.

Email Address Format

Every email address follows the format: username@domain.com

Example: rajesh.kumar@gov.in — here “rajesh.kumar” is the username and “gov.in” is the government domain.

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Email Protocols — How Email Travels

Email doesn’t just magically reach the recipient. It uses specific protocols (rules) at each stage — sending, receiving, and storing.

SMTP — Simple Mail Transfer Protocol

SMTP is the protocol used for sending emails from your device to the mail server and between mail servers.

• Port: 25 (default) or 587 (secure/TLS)
• SMTP only sends — it cannot receive or download emails
• Works like a post office that picks up and delivers your letter

POP3 — Post Office Protocol version 3

POP3 is used to receive/download emails from the mail server to your local device.

• Port: 110 (default) or 995 (secure/SSL)
• Downloads emails and deletes them from the server (by default)
• Emails accessible only on the device where downloaded
• Best for: single-device use with limited internet

IMAP — Internet Message Access Protocol

IMAP is used to receive/access emails while keeping them stored on the server.

• Port: 143 (default) or 993 (secure/SSL)
• Keeps emails on the server — sync across multiple devices
• Changes (read, delete, move) are reflected everywhere
• Best for: accessing email from phone, laptop, and tablet

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SMTP vs POP3 vs IMAP — Comparison Table

Exam Tip: SMTP = Sending Mail. POP3 = Picks and removes. IMAP = stays In the server.

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MIME — Multipurpose Internet Mail Extensions

MIME extends the capability of email beyond plain text. Without MIME, you could only send simple ASCII text messages.

MIME allows:

• Attachments — send files (PDF, images, documents)
• HTML emails — formatted text with colors, fonts, images
• Non-ASCII text — support for Hindi, Chinese, Arabic characters
• Multiple parts — text + attachment in one email

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Email Fields and Components

Exam Favourite: CC vs BCC — CC recipients are visible to everyone; BCC recipients are completely hidden from other recipients.

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Email Clients

An email client is software used to read, write, and manage emails.

Desktop Email Clients

Web-based Email (Webmail)

Webmail vs Desktop Client

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Microsoft Outlook — Key Features

Microsoft Outlook is the most widely used professional email client and is part of the Microsoft Office suite.

• Email Management — send, receive, organize into folders
• Calendar — schedule meetings, set reminders, share calendars
• Contacts — address book with details (phone, email, organization)
• Tasks — create to-do lists with deadlines
• Rules — auto-sort incoming emails (e.g., move newsletters to a folder)
• Junk Mail Filter — automatically detects and filters spam
• Out of Office (Auto-Reply) — sends automatic replies when you’re away
• PST files — Outlook stores data locally in .pst (Personal Storage Table) files

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Email Security

SPF — Sender Policy Framework

SPF is a DNS-based email authentication method that specifies which mail servers are authorized to send email on behalf of a domain.

• Prevents email spoofing (sending fake emails pretending to be from your domain)
• Domain owner publishes SPF record in DNS

DKIM — DomainKeys Identified Mail

DKIM adds a digital signature to outgoing emails, allowing the recipient’s server to verify the email was not tampered with during transit.

DMARC — Domain-based Message Authentication

DMARC builds on SPF and DKIM — tells receiving servers what to do if authentication fails (reject, quarantine, or allow).

MX Records

MX (Mail Exchange) records are DNS records that specify which mail server should receive email for a domain.

• Example: MX record for agridots.com points to mail.agridots.com
• Without MX records, email cannot be delivered to the domain

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Spam, Phishing & Email Threats

Protection Methods:

• Use spam filters (built into Gmail, Outlook)
• Never click suspicious links or download unknown attachments
• Check sender’s actual email address (not just display name)
• Enable two-factor authentication (2FA) on email accounts

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Mailing Lists, Forwarding & Auto-Reply

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Key Takeaways

• Email uses three protocols: SMTP (send), POP3 (download & delete), IMAP (sync & keep on server)
• SMTP port 25/587; POP3 port 110; IMAP port 143
• MIME enables attachments, HTML emails, and non-ASCII text
• CC is visible to all recipients; BCC is hidden
• Microsoft Outlook integrates email with calendar, contacts, and tasks
• SPF, DKIM, DMARC protect against email spoofing and phishing
• MX records in DNS direct email to the correct mail server
• Spam = junk mail; Phishing = fake emails to steal credentials

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Summary Cheat Sheet