Table of contents

What is email protocol?

What are the different email protocols?

Which protocol is right for you?



Common Email Protocols for Every Marketer to Know

Mashkoor Alam
ByMashkoor Alam

6 mins read

Emails are essentially used by businesses and individuals to alike for both professional and personal uses. On the surface, exchanging information or emails is a pretty simple process where the sender types in the message and sends it across to the recipient using the internet. In this article, you’ll learn about email protocols, the mechanism beneath the surface that defines this exchange and the different types of email protocols commonly used.

What is email protocol?

Email protocol is a set of rules that governs the exchange of emails between different clients, servers and devices. These protocols lay down the framework that emails should follow to be able to reach their intended recipients.

An image showing the processes involves in sending and receiving of an email

What are the different email protocols?

There are three most commonly used types of email protocols involved in exchange of emails.


Simple Mail Transfer Protocol (SMTP) is a text based protocol used in sending of the emails. It is responsible for transferring of the email from the sender’s computer to the sender’s email server and then from the sender’s email server to the recipient’s email server. SMTP establishes a TCP connection between the servers to deliver the email.

The entire process of sending the message from the one mail server to the other happens in three parts:

  • SMTP handshake
  • Email transfer
  • Termination of connection

SMTP uses only text commands and get’s replies from the other server in codes. Some of the most commonly used commands in SMTP are as follows.

  • HELO - introduces itself
  • MAIL FROM - specifies the sender of the email
  • RCPT TO - speicifies the recipient of the email
  • DATA - specifies the body of the email
  • RSET - resets the session but connection remains open
  • QUIT - closes the session
  • HELP - asks for help on commands
  • VRFY - verifies the address

A custom SMTP is helpful when you have an existing setup and wish to continue with it. It also allows you to manage deliverability on your own. Mailmodo is an all-in-one email marketing solution that allows you to set up custom SMTP.

2. POP3

Post Office Protocol version 3 (POP3) is used to access the emails stored on an email server. We saw how SMTP transferred the email from the sender’s computer to the recipient’s email server. It allows you to download the emails onto your local computer and read them.

Once the emails are downloaded to the local computer, they are by default, deleted from the server and cannot be accessed from any other device apart from the one they were downloaded onto. The upside to this is that you can view your emails on the device even when you are not connected to the internet. Although, if you do want to save a copy of the email on the server, you need to choose that option explicitly.

how-pop3-works-1024x544.png Source: Siteground

Like SMTP, POP3 also understands a simple set of text commands. Some of the commonly used commands are given below with their function.

  • USER - to enter user ID
  • PASS - to enter password
  • QUIT - closes the session
  • LIST - list the messages and their size
  • RETR - retrieve a message, pass it a message number
  • DELE - delete a message, pass it a message number


Internet Message Access Protocol (IMAP) is similar to POP3 as it is also used to access the emails stored on the email server. Unlike POP3, IMAP allows you to access these emails from multiple devices.

The user can see the headers of the emails and download the emails on demand when he chooses to view them. Also, in IMAP, the emails are stored on the server by default unless they’re deleted by the user. IMAP also allows you to organize your emails into folders, which are viewable from other devices too as the changes are made on the server.

IMAP protocol

Some of the common IMAP commands are given below, along with their functions.

  • IMAP_LOGIN - opens up a connection
  • SELECT - selects a mailbox to access the messages
  • EXAMINE - same as select without access to editing capabilities
  • CREATE - create a mailbox with a specified name
  • DELETE - delete a message
  • RENAME - change the name of a mailbox
  • LOGOUT - close the session

Which protocol is right for you?

For sending emails, you don’t essentially have options to choose from apart from SMTP. Conversely, POP3 and IMAP perform similar functions so it might be difficult for you to make a choice.

There are some key differences between the way these two protocols work. So you should be picking IMAP if you need to access your emails from different devices, need advanced management features like creating and managing folders and have a fast and reliable internet connection.

On the contrary, if you have an unstable internet connection, and do not require access from multiple devices, maybe because you’re the sole user and use a single device and prioritize privacy over accessibility, POP3 is the right protocol for you.


Multipurpose Internet Mail Extension Protocol (MIME) is another kind of protocol that allows email clients to send and receive non-textual content like multimedia files, images, audio, videos, etc. and without any size limitation. It also allows for the inclusion of multiple attachments in emails.

MIME is used in sending of multiple files in a single message. The messages are do not have a character limit. It also supports variety of content types as well as languages. It even allows for sending of interactive emails with designed using HTML, CSS, etc.

When sending an email with MIME, a MIME header is added to the header of the email. This contains various information.

  • MIME version - defines the version of the MIME used which is 1.1 currently
  • Content type - defines the type of data used in the body of the message using type and subtype. For example, Image/JPEG, Video/MPEG, Text/HTML
  • Content transfer encoding - defines the method used to encode the messages like 7-bit, 8-bit, binary, etc.
  • Content ID - Identities the whole message
  • Content description - defines whether the body is an image, video or audio


It is evident how email protocols play a foundational role in enabling seamless and efficient communication. As we continue to evolve in our technology, email protocols will also evolve further enhancing and enriching the email experience.

What you should do next

Hey there, thanks for reading till the end. Here are 3 ways we can help you grow your business:

  1. Talk to an email expert. Need someone to take your email marketing to the next level? Mailmodo’s experts are here for you. Schedule a 30-minute email consultation. Don’t worry, it’s on the house. Book a meet here.

  2. Send emails that bring higher conversions. Mailmodo is an ESP that helps you to create and send app-like interactive emails with forms, carts, calendars, games, and other widgets for higher conversions. Get started for free.

  3. Check out our AI prompts library. If you need AI prompts for ChatGPT or Bing, here's a ready-made database we’ve built to help marketers succeed at prompt engineering. Get your AI prompts here.

  4. Get smarter with our email resources. Explore all our knowledge base here and learn about email marketing, marketing strategies, best practices, growth hacks, case studies, templates, and more. Access guides here.

Frequently asked questions

The different protocols used in email are SMTP (Simple Mail Transfer Protocol), POP3 (Post Office Protocol 3) and IMAP (Internet Message Access Protocol).

SMTP is called push protocol because it pushes outgoing email from the sender's mail server to the recipient's mail server without the recipient's server requesting it.

The MIME protocol is needed because SMTP, IMAP, and POP3 primarily deal with the transfer and retrieval of plain text emails. However, modern emails often contain multimedia elements, attachments, and non-textual content.

Share this article
copy link
Linkedin logo
Twitter logo
Facebook logo
Whatsapp logo
Pinterest logo
mail logo

What should you do next?

Thanks for reading till the end. Here are 3 ways we can help you grow your business:

Get smarter with our email resources

Explore our email marketing guides, ebooks and other resources to master email marketing.

Do better email marketing with Mailmodo

Send app-like interactive emails with forms, carts, calendars, games, etc. to boost email ROI.

Talk to an email expert

Get a 30-min. free email consultation with a Mailmodo expert to optimize your email marketing.

with interactive emails

Get super-awesome email engagement

Get better ROI
on every email
you send

Quotation markMailmodo is a growth hack
for my business

Vineet Khare,
Bella Vita Organic

Get 3X conversions
with interactive emails


Create & send interactive emails without coding


Put revenue on auto-pilot with pre-built journeys


Save time with AI-powered email content creation

1000+ businesses grew with Mailmodo, including