Email Protocols

SMTP (Simple Mail Transfer Protocol)

• Purpose: Sending email
• Port: 25 (default), 587 (submission), 465 (SMTPS)
• How it works:
  • Client connects to SMTP server
  • Handshake with EHLO/HELO command
  • MAIL FROM, RCPT TO commands
  • DATA command to send message body
  • QUIT to close connection

SMTP Commands

HELO/EHLO - Identify the client
MAIL FROM - Specify sender
RCPT TO - Specify recipient
DATA - Begin message content
QUIT - Close connection

POP3 (Post Office Protocol v3)

• Purpose: Retrieving email
• Port: 110 (default), 995 (POP3S)
• Characteristics:
  • Downloads emails from server to client
  • Typically deletes from server after download
  • Good for single device access

IMAP (Internet Message Access Protocol)

• Purpose: Accessing and managing email on server
• Port: 143 (default), 993 (IMAPS)
• Characteristics:
  • Keeps emails on server
  • Supports folders and synchronization
  • Better for multi-device access
  • Can read email without downloading

Protocol Comparison

Feature	SMTP	POP3	IMAP
Purpose	Send	Receive	Access
Storage	N/A	Local	Server
Sync	N/A	No	Yes
Multi-device	N/A	Poor	Excellent