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SMTP vs. IMAP—What's the Difference Between These Email Protocols?

SMTP vs. IMAP – What’s the Difference Between These Email Protocols? There are significant differences between the two protocols involved in transmitting electronic messages.

  SMTP vs. IMAP – What’s the Difference Between These Email Protocols? There are significant differences between the two protocols involved in transmitting electronic messages. In this article, we’ll look at what the SMTP email protocol is, then introduce IMAP and compare them in detail.

What is an agreement?

Protocols are involved when communicating through electronic devices. They are a standardized set of rules applicable to these types of communication methods. It is convenient and efficient for two devices to communicate using the same protocol.

TCP/IP, Hypertext Transfer Protocol (HTTP), User Datagram Protocol (UDP), File Transfer Protocol (FTP), Internet Message Access Protocol (IMAP), and Simple Mail Transfer Protocol (SMTP) are some of the widely used communications protocol.

The following three main protocols are used in email communication and are supported by most browsers.

  • Simple Mail Transfer Protocol (SMTP)
  • Internet Message Access Protocol (IMAP)
  • Post Office Protocol (POP).

In this SMTP vs IMAP article, we will discuss the differences between the SMTP and IMAP protocols.

email newsletter

There are three main areas involved in the email communication process, as follows.

  • Sender – the person who initiated the email 
  • Recipient  – the person who received the message
  • Mail server  – an intermediate entity responsible for receiving and routing email

When a sender sends an email, it goes directly to the email server. The email server then helps the recipient to receive the specific email. After a successful connection is made, the next key is the email protocol, as it defines the standard for the connection.

What is SMTP?

SMTP stands for Simple Mail Transfer Protocol. Mainly used for sending emails from email clients to email servers. It is the recommended industry standard protocol among all email protocols. Use this protocol after drafting an email and issuing a send order. The SMTP server is mainly used to set communication rules between servers.


There are two types of SMTP servers involved in communication. They are relays and receivers. Relays are used to accept and route specific emails from senders to recipients. Meanwhile, the receiver is the server that receives the mail from the relay and delivers the mail to the recipient’s mailbox. It is important to mention that it is used between servers to transfer information.

An SMTP server can also be configured to act as an email gateway. SMTP users can provide instructions to the SMTP server on how to complete the email transmission.

SMTP communication is done in three main phases.

  • SMTP handshake – this is where the SMTP client connects with the respected SMTP server
  • Email Transport – Release Email
  • Terminate – Client-server communication ends here.

In the next section on SMTP vs. IMAP — what’s the difference between these email protocols? We’ll introduce the IMAP email protocol.

SMTP function

  • For “mail relay”.
  • SMTP supports several communication methods. For example, you can send audio, video, other media files, and a single message to multiple clients.
  • An interesting feature of SMTP is its error handling capabilities. It successfully responds to bad requests by taking the necessary action.
  • It provides certain conditions for mail forwarding.
  • The SMTP server can be configured as an email gateway.

What is IMAP?

IMAP stands for Internet Access Messaging Protocol. It is also known as Temporary Mail Access Protocol, Interactive Mail Access Protocol, and Internet Mail Access Protocol. This protocol only manages e-mail and deals with retrieving e-mail from the server. IMAP is not used for sending emails as it involves retrieving emails. However, it is the most commonly used protocol in retrieving email.


IMAP manages multiple mailboxes and organizes them into several categories. Second, it helps track messages by assigning flags to identify seen messages. Third, IMAP can identify mail to retrieve before downloading it to the mail server. Fourth, it keeps emails on a remote email server, limiting mailbox size. Therefore, IMAP is not recommended if you need to keep copies of a large number of emails. However, you can always upgrade the storage as it is a limitation on the mail server side. Interestingly, it only works for communication between client and server.

The flow of IMAP is as follows.

  • The recipient’s email client connects to the server where the message resides.
  • Recipients can see message headers on the server.
  • Once you get a successful response from the SPTP transfer, the recipient’s email client will use IMAP to fetch the message and save it in the recipient’s inbox.
  • When the recipient selects the exact message and starts reading it, IMAP downloads it for the recipient.

IMAP function

  • The main advantage of IMAP is that it allows email to be received on multiple devices. So multiple mailboxes are organized into different categories. So you can check it from any device after a successful login.
  • Also, you can easily download multiple media files using IMAP. On the other hand, you can’t download the entire message if you haven’t opened it. It is beneficial to have a robust startup process.
  • IMAP is ideal if you need to access email from different locations and your mailbox is managed by multiple users.
  • Provides a flag to track which messages are being viewed.
  • Another benefit is its ability to decide whether to retrieve emails from the mail server before downloading.
  • Downloading media is easy when attaching multiple files.

One downside of this mechanism is that it won’t perform correctly when the internet connection is bad, making it impossible for you to read your emails.

Next part on SMTP vs IMAP – what’s the difference between these email protocols? We will compare two solutions. 

What is the difference between SMTP and IMAP?


The main difference between SMTP and IMAP, and between SMTP and IMAP, is that each is used for different functions. 

  • SMTP stands for Simple Mail Transfer Protocol, and IMAP stands for Internet Access Messaging Protocol.
  • SMTP is used for sending messages only, while IMAP is used for managing and retrieving messages. Also, IMAP cannot be used to send messages.
  • SMTP can be used to transfer messages between a client and a server and between two servers. But IMAP only supports transferring messages from server to client.
  • SMTP allows you to organize email on client-side storage, while IMAP users have the flexibility to organize mail on the server.
  • SMTP works on port 25 (standard port for mail transfer), port 587 (TLS encrypted port), port 465 (non-RFC compliant port. You can use this port when you need to send secure messages using SMTP) and port 2525 ( Although this port is not a standard port, it is generally used by any email service. You can use it when you need to send non-encrypted emails. On the other hand, IMAP runs on port 993 (secure TLS/SSL port) for security connection.It is also called IMAPS and port 143 (which is the default port for IMAP).
  • IMAP gives users a lot of flexibility and access through multiple devices, while SMTP allows emails to be changed after they have been successfully sent.

What is the difference between the email protocols SMTP and IMAP? in conclusion

What did we learn from SMTP vs. IMAP — what’s the difference between these email protocols?

SMTP and IMAP are the two main TCP/IP protocols in wide use. It’s best not to use them alone. More importantly, they work together to send and retrieve messages/emails by establishing a connection between the sender, receiver, and email server.

email flow

  • Create an email and click send. Email clients will use SMTP to send mail to respected email servers.
  • The email server uses SMTP to send the message to the recipient’s email server.
  • After getting a successful response from the second step, IMAP is used to fetch the email from the email client and save it in the email box for further reference.

SMTP is an industry standard protocol for sending email. Therefore, you use this solution instead of IMAP, since that’s the main function of SMTP. On the other hand, IMAP is the most common protocol for receiving email. Interestingly, IMAP syncs messages across all devices.

All in all, IMAP is the best solution for anytime, anywhere access and when users need to access their mailboxes from multiple devices. Both protocols are commonly used to obtain a complete solution.

We want to make it easier for you to determine when, where, and how to use SMTP and IMAP.

Recommended reading:

How to enable SMTP, POP3 and IMAP of Naver email account

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