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Understanding SMTP, POP3, and IMAP in Email Services

Understanding SMTP, POP3, and IMAP in Email Services
Understanding SMTP, POP3, and IMAP in Email Services

CDN BizUnderstanding SMTP, POP3, and IMAP in Email Services. Surely most internet users, including those of you, are already accustomed to using communication technologies such as email.

Have you ever wondered what exactly does email works like? Check out this email guide for beginners below!

In this article, we will review how email services work by understanding the meaning of SMTP, POP3, and IMAP.

Understanding the Protocol in Email

Before discussing SMTP, POP3, and IMAP, you need to know what protocols are.

When a computer communicates with another computer, it is necessary to have rules and instructions that are followed by each computer. This term is called a protocol.

The protocols that we will review here are related to sending and receiving emails, namely SMTP, POP3, and IMAP. Below is an explanation of each of these protocols.

Understanding SMTP and POP3

Before getting into the discussion of IMAP, you will get an explanation of SMTP and its default port below.

What is SMTP?

Simple Mail Transfer Protocol or SMTP is a protocol for communicating with servers in order to send an email from a local email to the server, before finally being sent to the recipient’s email server. This process is controlled by the Mail Transfer Agent (MTA) on your e-mail server.

Default SMTP Port

Port 25 – Unencrypted port
Port 426 – SSL / TLS port, otherwise known as SMTPS

What is POP3?

POP3 (Post Office Protocol 3) is the latest version of the standard protocol for receiving email. POP3 is a client/server protocol where e-mail is sent from the server to the local e-mail. Used to communicate with the e-mail server and download all e-mail to local e-mail (such as Outlook, Thunderbird, Windows Mail, Mac Mail, and so on), without storing a copy on the server. Usually, in the e-mail application, there is an option to keep a copy of the downloaded e-mail on the server or not.

If you access the same email account from different devices, we highly recommend that you keep a backup. This needs to be done as a precaution if the second device does not download the email, while the first device has deleted it.

POP3 is a one-way communication protocol, which means data is retrieved from the server and sent to a local e-mail on your computer device.

Default POP3 port

Port 110 – Unencrypted port
Port 995 – SSL / TLS port, other names POP3S

Pros of Using POP3

  • Once the email has been downloaded through the local mail application on your computer, you don’t need to be connected to the internet if you want to open it again.
  • Mostly there is no size limit for e-mails sent and received.
  • Can open attachment files quickly.
  • There is no maximum size for a mailbox unless your computer hard drive is full.

Cons of Using POP3

  • If JavaScript in the e-mail reader is enabled, phishing e-mails with embedded JavaScript can be read in the e-mail.
  • All messages will be saved on the computer. This can reduce space on the computer’s hard drive.
  • All attachment files are downloaded and stored on the computer. Therefore, the potential for computers to be infected with viruses from email is greater.
  • Email folders sometimes get lost. If this is the case, the restoration attempt is quite difficult.

What is IMAP and how it differs from POP3?

IMAP (Internet Message Access Protocol), like POP3, is also used to send email to local mail, it’s just that there is a slight difference in how it works.

IMAP is a two-way communication protocol in which changes are made to local mail sent to the server. Basically, the contents of the e-mail remain on the server. The IMAP protocol is recommended by email providers like Gmail over POP3.

In IMAP, e-mail is stored on a server. when you will check e-mail, local mail will contact the server to display e-mail messages. So that the e-mail message files remain on the server and are not downloaded to local e-mail.

Default IMAP port

Port 143 – Unencrypted port
Port 993 – SSL / TLS port, another name for IMAPS

Pros of Using IMAP

  • You can access your email from anywhere via different devices.
  • Email can be accessed via a web browser without an email application.
  • You only download the messages you want to open, so you don’t have to wait for all of them to download.
  • Attachments are not automatically downloaded by IMAP, so email can be accessed more quickly. You can also select specific attachments that you want to open.
  • A large number of mobile users today has resulted in more use of IMAP. This is because the files of the e-mail messages are stored on the server and you only have to access them.

Cons of Using IMAP

  • There are several hosting services that do not support IMAP.
  • Email is stored on the server thereby reducing disk space hosting.
  • An email with IMAP can only be accessed when connected to the internet.


We hope that by now you have a better understanding of the protocol on e-mail and the ports used with a little explanation about the meaning of SMTP, POP3 and IMAP. You have also seen that POP3 and IMAP have basically the same function, and only have slight differences.

In IMAP, e-mail content is stored on the server. Meanwhile, POP3 downloads all emails to the computer. On the other hand, we’ve covered the default ports for SMTP, POP3, and IMAP.


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