Mail Protocols

These protocols are used for sending, receiving, and managing email across networks, each offering different features for message retrieval and delivery.

Protocol

Description

Use Case

IMAP (Internet Message Access Protocol)

Allows clients to access and manipulate emails stored on a mail server. Supports synchronization across multiple devices and folder management.

Accessing and managing email from multiple devices

POP3 (Post Office Protocol version 3)

Simple protocol for downloading emails from the server to a local client. Typically removes messages from the server after download.

Retrieving email on a single device with offline access

SMTP (Simple Mail Transfer Protocol)

Standard protocol for sending email between clients and servers. Handles outgoing mail and server-to-server relay.

Sending email messages over the internet

RFC: RFC 3501

Main Features:

  • Access and manage email stored on a mail server

  • Supports folder structures, message flags, and partial message fetch

  • Allows synchronization across multiple devices

Use Cases:

  • Multi-device email access (desktop, webmail, mobile)

  • Server-side mailbox management and search

  • Consistent mailbox state across devices

Alternative Protocols:

  • POP3 – Simpler, single-device email access without sync

Let us learn more about IMAP:

Jump to “IMAP”

RFC: RFC 1939

Main Features:

  • Downloads email from server to client device

  • Typically deletes messages from the server after download

  • Lightweight and easy to implement

Use Cases:

  • Offline email access on single device

  • Environments with limited storage or no constant internet

Alternative Protocols:

  • IMAP – For synchronized, server-based access and multi-device use

Let us learn more about POP3:

Jump to “POP3”

RFC: RFC 5321

Main Features:

  • Used for sending and relaying email messages

  • Supports authentication and encryption (via ESMTP, STARTTLS, etc.)

  • Queues and forwards email between MTAs (Mail Transfer Agents)

Use Cases:

  • Sending email from client to mail server

  • Server-to-server transmission of outgoing email

  • Bulk email services and email relays

Alternative Protocols:

  • SMTP is the universal standard; no widely used alternatives

Let us learn more about SMTP:

Jump to “SMTP”