POP3 vs IMAP: which protocol allows you to receive email on any device. What is the difference between POP3 and IMAP?

The workstation may not have sufficient resources to ensure continuous operation of the SMTP server. It is too expensive for home computers to maintain a connection to the Internet around the clock.

But access to e-mail is necessary both for such small nodes and for individual computers. A protocol has been developed to solve this problem. POP3(Post Office Protocol - Version 3, STD: 53. M. Rose, RFC-1939). This protocol provides host access to the underlying mail server.

POP3 It does not aim to provide a wide list of mail manipulations. Mail messages are received by the mail server and stored there until the application is launched on the client workstation POP3. This application establishes a connection to the server and retrieves messages from there. Mail messages on the server are erased.

The more advanced and complex IMAP4 protocol is discussed in RFC-2060 (port 143). You can read about POP3 authentication in RFC-1734.

In the future, the computer client will be called the machine using the POP3 services, and the computer server will be the party offering the POP3 services.

When a computer client user wants to send a message, he establishes an SMTP connection with the mail server directly and sends everything he needs through it. In this case, the POP3 computer server is not necessarily a mail server.

At the initial moment, the computer POP3 server listens to TCP port 110. If the computer client wants to use the services of the POP3 server, it establishes a TCP connection with it. Once the connection is established, the POP3 server sends a notification to the client (for example, +OK POP3 server ready) and the session enters the authorization phase (see also RFC-1734, -1957). After this, commands and responses can be exchanged.

POP3 commands consist of keywords (3-4 characters), which can be followed by arguments. Each command ends with a pair of CRLF characters. Both keywords and arguments can only contain printable ASCII characters. Space characters are used as delimiters. Each argument can be up to 40 characters.

The POP3 response signal contains a status indicator and a keyword, which may be followed by additional information. The response is also terminated with a CRLF code sequence. The response length does not exceed 512 characters, including CRLF. There are two status indicators: positive - "+OK" and negative - "- ERR" (all characters are uppercase).

Responses to some commands may contain several lines. In this case, the last line contains exit code 046 (".") followed by CRLF.

In practice, multiline responses are terminated with the sequence "CRLF.CRLF" to prevent imitation.

During the authorization process, the client must introduce itself to the server by passing a name and password (an option is to send the APOP command). If authorization is successfully completed, the session enters the transaction state (TRANSACTION). When a QUIT command is received from the client, the session goes into the UPDATE state, while all resources are released and the TCP connection is terminated.

The server responds to syntactically unrecognized and invalid commands by sending a negative status indicator.

The POP3 server can be equipped with a passive timer (10 minutes), which automatically interrupts the session. The arrival of any command from the client resets this timer to zero.

The server numbers all transmitted messages from its mailbox and determines their length. A positive response begins with +OK, followed by a space, the message number, another space, and the length of the message in octets. The response ends with the CRLF sequence. Sent messages are deleted from the server mailbox. All messages sent during a POP3 session must follow Internet message format guidelines.

In the transaction state, the client can send the server a sequence of POP3 commands, to each of which the server must send a response. The following is a brief description of the commands used in the state. transaction.

LIST[message]

Arguments: message number (optional), which cannot refer to a message marked as deleted. The command can only be issued in TRANSACTION mode. If the argument is present, the server issues a positive response containing the message information string. Such a line is called a message scan listing ( scan

Basic Operations

Initially, the server listens for a TCP connection on port 110. When a client wants to use the POP3 service, it must establish a connection to the server. After the connection is established, the server sends a hello to the client. The client and POP3 server exchange commands and responses (in that order) until the connection is closed or terminated. POP3 commands consist of a keyword, which can be followed by one or more parameters. All commands end with a CRLF pair. Keywords and arguments consist of printable ASCII characters. Keywords and arguments are separated by a single space. Keywords consist of 3 or 4 characters, each argument can be up to 40 characters long.
Responses consist of a status indicator and a keyword. All responses end with a CRLF pair. There are currently two status indicators: positive (+OK) and negative (-ERR).

Certain responses may be multi-line. In this case, after the first response line ending with CRLF, each additional line sent ends with a CRLF pair. After all response lines have been sent, the last line will end with a final octet - a character. (“.”, decimal code 46) and a CRLF pair. A POP3 session consists of several stages. After establishing a TCP connection, the server sends a hello and the session enters the AUTHORIZATION state. At this stage, the client must identify itself to the server. After successful identification, the session enters the TRANSACTION state. In this stage, the client requests execution of commands on the server. When the client sends the QUIT command, the session enters the UPDATE state. At this stage, the POP3 server releases all resources used in the TRANSACTION stage and ends its work. The TCP connection is then closed. A POP3 server MAY have an inactivity autologout timer (auto-terminate session timer when inactive). This timer MUST be set to a minimum of 10 minutes. If the client does not send commands to the server within the specified time interval, then the server closes the TCP connection without transitioning to the UPDATE state, i.e. without deleting messages or sending any responses to the client.

AUTHORIZATION state

After the client opens a TCP connection, the server sends a one-line hello. The line must end with CRLF.
Example:

S: +OK POP3 server ready

Note:
The POP3 server should always send a positive response as a greeting.

The session is now in the AUTHORIZATION state. The client must identify itself to the server. This document describes two methods, the combination of the USER and PASS commands and the APOP command. To authenticate using the USER and PASS commands, the client must first send the USER command. If the server responded with a positive status indicator (+OK), then the client must send a PASS command to complete authorization or send a QUIT command to end the session. If the server sent a negative response (-ERR) to the USER command, then you can repeat the authorization or end the session with the QUIT command.
After receiving the PASS command, the server uses the USER and PASS argument pair to determine access to the mailbox.
Once the server has determined through some authentication command that the client should be given access to the corresponding mailbox, the POP3 server gains exclusive access to the mailbox to prevent messages from being modified or deleted before the UPDATE state. If the blocking is successful, the server sends a positive response and a hello string. The session now enters the TRANSACTION state with no messages marked as deleted. If the mailbox cannot be opened for some reason (for example, the lock cannot be performed or the client is denied access to the corresponding mailbox), the server responds with a negative status indicator. After a negative response, the server can close the connection. If the server has not closed the connection, the client can send a new authentication command and start over, or send a QUIT command.
After the server has opened a mailbox, it assigns a number to each message and notes the message size in octets. The first message will be number 1, the next message will be number 2, and so on. In POP3 commands, all numbers are represented in decimal.

Here's a summary of the three teams reviewed so far:

USER name

Arguments:
Mailbox identification string (required).

Restrictions:
Can only be sent in the AUTHORIZATION state after a POP3 greeting or an unsuccessful USER or PASS command.

Possible answers:

OK name is a valid mailbox -ERR never heard of mailbox name

PASS string

Arguments:
mailbox password (required).

Restrictions:
Can only be passed in the AUTHORIZATION state after a successful USER command.

Details:
The PASS command has only one argument; the server may treat the space in the parameter as part of the password, instead of an argument separator.

Possible answers:

OK maildrop locked and ready -ERR invalid password -ERR unable to lock maildrop

C: USER mrose S: +OK mrose is a real hoopy frood C: PASS secret S: +OK mrose"s maildrop has 2 messages (320 octets) ... C: USER mrose S: +OK mrose is a real hoopy frood C: PASS secret S: -ERR maildrop already locked

QUIT

Arguments:
No

Restrictions:
No

Possible answers:

C: QUIT S: +OK dewey POP3 server signing off

TRANSACTION state

After the client has successfully identified itself to the server and the server has locked and opened the corresponding mailbox, the session enters the TRANSACTION state. The client can now request information. After each command, the server sends a response. At the end, the client sends the QUIT command and the session enters the UPDATE state.

STAT

Arguments:
No

Restrictions:

Details:
The POP3 server sends a positive response with a line containing information about the mailbox. This line is called "drop listing". For easy parsing, POP3 servers use a specific format for “drop listing”. A positive response includes: a status indicator (+OK), followed by the number of messages and message size in octets separated by a single space. Messages marked as deleted are not counted.

Possible answers:

C: STAT S: +OK 2 320

LIST message

Arguments:
Message number (optional), messages marked as deleted are not counted.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
If an argument is given, the server sends a positive response with a string of information for the given message. This line is called “scan listing”. If the argument is not given, then the server sends a multiline response. After the status indicator (+OK), for each message in the mailbox, the POP3 server sends a line containing information for that message. This line is called “scan listing”. All POP3 servers use a specific format for “scan listing”. A “scan listing” consists of a message number followed by a single space and the exact size of the message in octets. This document does not specify what should follow the message length, the only requirement is that the response ends with a CRLF pair. Various extensions may include additional information.

Possible answers:

OK scan listing follows -ERR no such message

C: LIST S: +OK 2 messages (320 octets) S: 1,120 S: 2,200 S: . ... C: LIST 2 S: +OK 2 200 ... C: LIST 3 S: -ERR no such message, only 2 messages in maildrop

RETR message

Arguments:

Restrictions:
Can only be sent in TRANSACTION state.

Details:
If the response is positive, following the positive status indicator, the server sends a multi-line response containing the specified message.

Possible answers:

OK message follows -ERR no such message

DELE message

Arguments:
Message number (required), messages marked as deleted are not counted.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
The POP3 server marks the message as deleted. All subsequent calls to this message will generate an error. In fact, the server does not delete the message until the UPDATE condition occurs.

Possible answers:

OK message deleted -ERR no such message

C: DELE 1 S: +OK message 1 deleted ... C: DELE 2 S: -ERR message 2 already deleted

NOOP

Arguments:
No.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
The server does nothing and responds only positively.

Possible answers:

RSET

Arguments:
No.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
If the message was marked as deleted, the server removes this mark. The answer is always positive.
Possible answers:

UPDATE status

When a client sends a QUIT command in the TRANSACTION state, the server enters the UPDATE stage (Note that if the client sends a command in the AUTHORIZATION state, the server ends the session and does not enter the UPDATE stage). If the session is terminated for some other reason, without issuing a QUIT command, the POP3 session does not enter the UPDATE stage and no messages from the mailbox should be deleted.

QUIT

Arguments:
No.

Restrictions:
No.

Details:
The server deletes all messages marked as deleted. A response is sent. The TCP connection is closed.

Possible answers:

C: QUIT S: +OK dewey POP3 server signing off (maildrop empty) ... C: QUIT S: +OK dewey POP3 server signing off (2 messages left) ...

Optional Commands

The POP3 commands described above should be supported by all POP3 servers. Additional commands give the client greater freedom in processing messages. Note: This document encourages support for additional commands rather than adding additional information to “drop listing” and “scan listing”.

TOP message n

Arguments:
Message number (mandatory) and a non-negative number indicating the number of lines of the message body that the server will send to the client, the argument is required. You cannot access messages marked as deleted.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
After a positive response, the server sends a multiline response. After the initial +OK, the server sends the message header, an empty line, and the specified number of lines from the message body.

Note:
If the number of lines the client requests is greater than the number of lines in the message, then the server transmits the entire message.

Possible answers:

OK top of message follows -ERR no such message

C: TOP 1 10 S: +OK S: S: . ... C: TOP 100 3 S: -ERR no such message

UIDL message

Arguments:
Message number (optional). You cannot access a message marked as deleted.

Restrictions:
Can only be sent in TRANSACTION state.

Details:
If the argument is given, the server sends a positive response with a string containing information about the specified message. This line is called "unique-id listing".
If the argument is not specified, then if the response is positive, the server sends a multiline response. After the status indicator (+OK), and a line containing information about the message.
To simplify parsing, all servers must use a specific “unique-id listing” format. “unique-id listing” consists of the message number and unique identifier separated by a single space. The unique identifier must not be followed by any additional information.
A unique identifier is an arbitrary server-defined string containing characters in the range 0x21 to 0x7E that uniquely identifies a message within a mailbox. The ID is saved for the entire session. The server must not reuse the identifier for a given mailbox as long as there is an object using it. Messages marked as deleted are not taken into account.

Which is better: POP3 or IMAP is not just a matter of taste.

POP3 downloads all mail from the server to the local computer. In this case, mail, in most cases, is deleted from the server immediately after loading into the mail client, or after several days. This means that letters are located in only one place - either on the server or on the computer. If something happens to the computer, then you will face a problem.

However, POP3 is still the most common email download protocol. The abbreviation “POP” stands for “Post Office Protocol”. It works like a traditional post office. The difference between IMAP and POP3 is that the latter is like a postman who carries a letter from the office to your home. Naturally, if the letter is with you, it can no longer be in any other place.

When considering which is better: IMAP or POP3, give preference to the second option if you have little space allocated on the server, and getting additional megabytes would be too expensive. Most email service providers set a certain quota for the volume of correspondence. If it is exhausted, then you will be able to receive new emails only after deleting some of the old ones.

IMAP is a newer development. It stands for “Internet Message Access Protocol”, and, as the name suggests, it only provides access to messages on the server. The difference between IMAP and POP3 is that the first protocol first requests a list of messages stored on the mail server. Your email client then downloads local copies of the emails and allows you to work with them, but the emails themselves remain on the server until you explicitly delete them from there.

When choosing between POP3 or IMAP, first of all, you should answer the question of whether you are going to work with email from several devices or just one. If you read and send emails from your home or work computer, laptop, or tablet, your best bet is to rely on IMAP.

Almost all major email service providers (Gmail, Yahoo, Hotmail, etc.) support this protocol. Additionally, Microsoft Exchange is an IMAP variant. This protocol allows you to easily synchronize email between your smartphone, tablet and the computers you use. You will also be able to access your correspondence using a regular Internet browser. After all, emails are stored on the server, and many email service providers create a convenient interface for web access.

In a modern world filled with all kinds of digital gadgets, when choosing between POP3 and IMAP, it is better to give preference to the latter, newer protocol. With its help, we break the tight connection between the device, the email client and the email server. Now the location and type of operating system do not matter. And the reduction in the cost of data storage allows you to get mailboxes of huge volume at your disposal. Today, only a few providers allow you to use email only via the POP3 protocol. Unless you have any special reason to use POP3, choose the IMAP protocol.

This article covers the most commonly used Internet email protocols - POP3, IMAP, and SMTP. Each of them has a specific function and way of working. The content of the article explains which configuration is best suited for the user's specific needs when using an e-mail client. It also reveals the answer to the question of what protocol e-mail supports.

What is POP3?

Protocol Version 3 (POP3) is a standard email protocol used to receive email from a remote server to a local email client. Allows you to download messages to your local computer and read them even if the user is offline. Please note that when you use POP3 to connect to your account, messages are downloaded locally and deleted from the email server.

By default, the POP3 protocol runs on two ports:

port 110 is an unencrypted POP3 port;

port 995 - this should be used if you want to connect to POP3 securely.

What is IMAP?

Internet Message Access Protocol (IMAP) is a protocol for receiving email messages, used to access email on a remote web server from a local client. IMAP and POP3 are the two most commonly used protocols for receiving emails and are supported by all modern email clients and web servers.

The POP3 protocol means that your email address is accessible only from one application, while IMAP allows simultaneous login from several clients at once. This is why IMAP is better if you're going to be accessing your email from different places or if your messages are managed by multiple users.

The IMAP protocol runs on two ports:

port 143 is the default unencrypted IMAP port;

port 993 - this must be used if you want to connect securely using IMAP.

What is SMTP?

The protocol is a standard protocol for sending email over the Internet.

SMTP operates on three ports:

port 25 is unencrypted by default;

port 2525 - this is opened on all SiteGround servers if port 25 is filtered (for example by your ISP) and you want to send unencrypted emails using SMTP;

port 465 - This is used if you want to send messages securely using SMTP.

What protocols are used to exchange email? Concepts and terms

The term email server refers to the two servers required to send and receive emails, i.e. SMTP and POP.

The incoming mail server is the server associated with your email address account. It cannot have more than one incoming mail server. To access incoming messages, you need an email client—a program that can receive email from an account, allowing the user to read, forward, delete, and reply to messages. Depending on your server, you may be able to use a dedicated email client (such as Outlook Express) or a web browser. Thus, Internet Explorer is used to access email-based accounts. Messages are stored on the incoming mail server until it is downloaded. Once you have downloaded your mail from the mail server, you cannot do it again. To successfully download data, you must enter the correct settings in your email program. Most incoming mail servers use one of the following protocols: IMAP, POP3, HTTP.

Outgoing mail server (SMTP)

This is a server used only for sending emails (to transfer them from your email client program to the receiver). Most outgoing mail servers use Protocol) to send correspondence. Depending on your network settings, the outgoing mail server may belong to your ISP or the server where you set up your account. Alternatively, you can use a subscription-based SMTP server that will allow you to send emails from any account. Due to spam issues, most outgoing email servers do not allow you to send emails unless you are logged into their network. A server with an open relay will allow you to use it to send emails, whether you belong to its network group or not.

Email Ports

For networks, a port means the end point of a logical connection. The port number determines its type. The following are the default email ports:

POP3 - port 110;

IMAP - port 143;

SMTP - port 25;

HTTP - port 80;

secure SMTP (SSMTP) - port 465;

secure IMAP (IMAP4-SSL) - port 585;

IMAP4 over SSL (IMAPS) - port 993;

Secure POP3 (SSL-POP) - port 995.

Email protocols: IMAP, POP3, SMTP and HTTP

Basically, a protocol refers to a standard method used at each end of a communication channel. To deal with email, you must use a special client to access the mail server. In turn, they can exchange information with each other using completely different protocols.

IMAP protocol

IMAP (Internet Message Access Protocol) is a standard protocol for accessing email from your local server. IMAP is a client/server protocol in which email is received and data is stored by your Internet server. Since it only requires a small data transfer, it works well even on a slow connection, such as a modem connection. When attempting to read a particular email message, the client downloads data from the server. You can also create and manage folders or mailboxes on the server, and delete messages.

POP3 protocol

POP (Post Office Protocol 3) provides a simple, standardized way for users to access their mailboxes and download messages to their computers.

When using POP, all your email messages will be downloaded from the mail server to your local computer. You can also leave copies of your emails on the server. The advantage is that after downloading your messages, you can disconnect your Internet connection and read your email at your leisure without incurring additional communication costs. On the other hand, with this protocol you receive and download a lot of unwanted messages (including spam or viruses).

SMTP protocol

The protocol is used by a mail transfer agent (MTA) to deliver electronic messages to a specific recipient server. SMTP can only be used to send emails, not to receive them. Depending on your network or ISP settings, you may only be able to use the SMTP protocol under certain conditions.

HTTP protocols

HTTP is not a protocol designed for email communications, but it can be used to access your mailbox. It is also often called web email. It can be used to compose or receive emails from your account. Hotmail is a good example of using HTTP as an email protocol.

Managed File Transfers and Network Solutions

Your ability to send and receive email is primarily due to three TCP protocols. They are SMTP, IMAP and POP3.

SMTP

Let's start with SMTP because its main function is different from the other two. SMTP, or Simple Mail Transfer Protocol, is primarily used to send email from an email client (such as Microsoft Outlook, Thunderbird, or Apple Mail) to an email server. It is also used to relay or forward mail messages from one mail server to another. This is necessary if the sender and recipient have different email service providers.

SMTP, which is specified in RFC 5321, uses port 25 by default. It can also use port 587 and port 465. The latter, which was introduced as the port of choice for secure SMTP (a.k.a. SMTPS), is considered deprecated. But in fact, it is still used by several email service providers.

POP3

The Post Office Protocol, or POP, is used to retrieve email messages from the latest version that is widely used is version 3, hence the term "POP3".

POP version 3, specified in RFC 1939, supports extensions and several authentication mechanisms. Authentication features are required to prevent malicious users from accessing user communications.

The POP3 client receives email as follows:

connects to the mail server on port 110 (or 995 for SSL/TLS connections);

deletes copies of messages stored on the server;

disconnects from the server.

Although POP clients can be configured to allow the server to continue to store copies of downloaded messages, the steps above are common practice.

IMAP

IMAP, especially the current version (IMAP4), is a more complex protocol. This allows users to group related messages and place them in folders, which in turn can be organized hierarchically. It is also equipped with message flags that indicate whether the message has been read, deleted, or received. It even allows users to search server mailboxes.

Operating logic (imap4 settings):

connects to the mail server via port 143 (or 993 for SSL/TLS connections);
retrieves email messages;
serves to connect before closing the mail client application and download messages on demand.

Please note that messages are not deleted on the server. This can have serious consequences. IMAP specifications can be found in RFC 3501.

Choosing between IMAP and POP3

Since the core function of SMTP is fundamentally different, the dilemma of choosing the best protocol usually involves only IMAP and POP3.

If server storage space is important to you, then choose POP3. A server with limited memory is one of the main factors that may force you to support POP3. Because IMAP leaves messages on the server, it can consume memory space faster than POP3.

If you want to access your mail at any time, then it is better to stick with IMAP. There is one good reason why IMAP was designed to store messages on a server. It is used to search for messages from multiple devices - sometimes even simultaneously. So if you have an iPhone, Android tablet, laptop, and desktop and want to read email from any or all of these devices, then IMAP is the best choice.

Synchronization is another advantage of IMAP. If you access email messages from multiple devices, you'll likely want them all to show any activity you've performed.

For example, if you read messages A, B, and C, you want them to also be marked as read on other devices. If you deleted letters B and C, you will want the same messages to be deleted from your inbox on all gadgets. All these synchronizations can only be achieved if you use IMAP.

Since IMAP allows users to organize messages hierarchically and place them in folders, it helps users better organize their correspondence.

Of course, all IMAP functionality comes at a price. These solutions are more difficult to implement and the protocol ends up consuming a lot more CPU and RAM, especially when it performs the synchronization process. In fact, high CPU and memory usage can happen on both the client and server side if there are a ton of messages to sync. From this point of view, the POP3 protocol is less expensive, although less functional.

Privacy is also one of the issues that will greatly depend on the end users. They would generally prefer to download all email messages and not leave copies of them on an unknown server.

Speed is an advantage that varies and depends on the situation. POP3 has the ability to download all mail messages when connected. And IMAP can, if necessary (for example, when there is insufficient traffic), download only message headers or certain parts and leave attachments on the server. Only when the user decides that the remaining parts are worth downloading will they become available to him. Therefore, IMAP can be considered faster.

However, if all messages on the server must be downloaded every time, then POP3 will be much faster.

As you can see, each of the described protocols has its own advantages and disadvantages. It's up to you to decide which features or capabilities are more important.

Also, the desired method of accessing the e-mail client determines the preferred protocol. Users who only work from one machine and use webmail to access their new emails will appreciate POP3.

However, users who share mailboxes or access their emails from different computers will prefer IMAP.

Spam firewalls with SMTP, IMAP and POP3

Most spam firewalls only deal with and protect the SMTP protocol. The servers send and receive SMTP email and these will be checked by the spam firewall on the gateway. However, some spam firewalls provide the ability to protect POP3 and IMAP4 when external users need these services to access their email.

SMTP firewalls are transparent to end users; There are no configuration changes for clients. Users still receive and send email messages to the email server. Thus, Exchange or Dominos must configure routing of messages to the firewall based on a proxy server when sending email, and also provide the ability to send emails from the firewall.

It is unlikely that there is at least one person actively using the Internet who does not have an email. Indeed, having an e-mail makes it easier to maintain correspondence, and is also a prerequisite for using many virtual services - from social networks to registering on a website or subscribing to its updates.

If he talks about using e-mail for its intended purpose, then all you need to do is open any browser, go to the postal service website and log in to read new letters. But there is also the possibility of viewing correspondence without a browser - using a special email client. And for this, 2 mail protocols are used - IMAP and POP3.

How is POP3 different from IMAP?

The technical difference between the POP3 and IMAP protocols is generally not significant. Both of them are application layer Internet protocols using ports 110 and 143 respectively to access the server via TCP/IP. The purpose of the protocols is actually the same, but they perform it in slightly different ways. And in order to more accurately understand how POP3 differs from IMAP, you need to understand in more detail the principle of their operation.

Mail clients working with the POP3 protocol allow you to download files from a mail server at a time, and they connect to the network just for this purpose. This means that further work with electronic correspondence occurs without using the network.

Email clients that use the IMAP protocol can work without a network connection, but access to it greatly expands their capabilities. As a result, the client can independently choose which letters need to be downloaded to the local machine, whereas when using the POP3 protocol, all letters are downloaded, after which unnecessary ones are deleted.

Due to the fact that the POP3 client only downloads files, and further work is carried out offline, it works a little faster. The IMAP client requires more resources because it is online. It is also worth noting another significant difference between POP and IMAP, for which many email services, including Yandex, prefer the latter - multi-user mode. The IMAP protocol allows multiple clients to connect to the server, while POP3 only allows single-user mode.

So let's summarize what are the differences between IMAP and POP3:

they use different ports to work with the server - 110 for POP3 and 143 for IMAP;
POP3 works only in offline mode, IMAP can work both offline and online;
to work with files and messages using the POP3 protocol, you need to download them to your local computer, but IMAP allows you to work with them directly on the server;
POP3 has faster server access than IMAP;
IMAP allows you to configure the separation of access rights, while POP3 does not have this option.

Now you know the difference between POP and IMAP. In conclusion, it is worth noting that at the moment the use of the POP3 protocol is more common on the network due to its ease of configuration. However, IMAP is rapidly gaining popularity, primarily when dealing with electronic correspondence using mobile devices. In general, many email services combine the use of these protocols, depending on the needs of the client and the device he is using.