A fairly complete description of the POP3 protocol.

POP3 port (the protocol is a standard Internet application layer protocol used by local e-mail clients to retrieve data from remote server over a TCP/IP connection.

POP3 is used to communicate with a remote mail server and download Email to a local mail client. If you are referring to the same account With different devices, it is recommended to save remote copies, because otherwise your second device will not download emails if the first one has already deleted them. It's also worth mentioning that POP3 is one-way which means data is retrieved from a remote server and sent to a local client.

POP3 Port: Technology Overview

The POP protocol supports download and delete requirements for accessing remote mailboxes (called maildrop in the POP RFC). While most clients have the ability to leave mail on the server after download, email applications using POP typically connect, receive all messages, save them to the user's PC as new messages, delete them from the server, and then disconnect.

Other protocols, such as IMAP (Internet Message Access Protocol), provide more complete and sophisticated remote access to common mailbox operations. In the late 1990s and early 2000s, fewer ISPs supported IMAP due to the storage space required on hardware service provider.

Modern e-mail clients support POP. Over time, popular email software added support for IMAP.

Technical features

The server works with famous port 110. POP3 is the latest standard general use. Encrypted communication for the protocol is requested using the STLS or POP3S command, which connects to the server using Transport Layer Security (TLS) or Secure Sockets Layer (SSL).

Available messages to the client are captured when the mailbox server is authenticated against the message number by the session-local unique identifier assigned to the message. This setting is persistent and unique to maildrop and allows the client to access the same message in different sessions. Mail is retrieved and marked for deletion by message number. When a client logs out of a session, mail marked for deletion is removed from the maildrop.

History and documentation

The first version (POP1) was specified in RFC 918 (1984), POP2 in RFC 937 (1985). POP3 was initiated by RFC 1081 (1988). Its current RFC 1939 specification has been updated with the RFC 2449 extension mechanism and the authentication mechanism in RFC 1734.

POP3 currently supports multiple authentication methods to provide varying levels of protection against illegal access to a user's email. Most of these are provided by the POP3 extension mechanisms. Clients support SASL authentication methods through the AUTH extension. The MIT Athena project has also released a version of Kerberized. RFC 1460 introduced APOP to the core protocol. APOP is a challenge/response protocol that uses the MD5 hash function to avoid retries and privacy violations.

POP4 only exists as an unofficial proposal adding basic management folders, support for multiple messages, and message flag management to compete with IMAP. The POP4 version has not been developed since 2003.

Extensions and specifications

A mechanism was proposed in RFC 2449 for hosting common extensions as well as organized support additional commands, such as TOP and UIDL. The RFC does not intend to encourage extensions and has confirmed that the role of POP3 is to provide simple support primarily for downloading and removing mailbox handling requirements.

Extensions are called features in the official documentation and are listed by the CAPA team. With the exception of APOP, optional commands have been included in the initial feature set.

STARTTLS and SDPS extensions

This extension allows you to use the Transport Layer Security or Secure Sockets Layer protocol using the STLS command on standard port POP3, not alternative. Some clients and servers use the method alternative port, which uses TCP port 995 (POP3S).

Demon Internet introduced an extension to POP3 that allowed multiple accounts to be attached to the same domain, and became known as the Standard POP3 Dial-Up Service (SDPS). To access each account, the login includes a hostname, like john@hostname or john+hostname.

Kerberized Post Office Protocol

When computed, local email clients can use the Kerberized Post Office Protocol (KPOP) Internet protocol to retrieve email from a remote server over a TCP/IP connection. The KPOP protocol is based on the POP3 protocol with the differences that it adds Kerberos security and runs on TCP port number 1109 instead of 110 by default. One version software for the mail server is located on the Cyrus IMAP server.

Comparison with IMAP

The POP3 SSL port is a much simpler protocol that simplifies implementation. Mail moves the message from the email server to your local computer, although it is usually possible to leave messages on the email server.

IMAP by default leaves the message on the email server by simply downloading a local copy.

POP treats a mailbox like a single store and has no concept of folders.

IMAP client makes complex requests, queries server for headers or content certain messages or searches for emails that match certain criteria. Messages in the mail repository can be marked with various status flags (such as "deleted" or "replies"), and they remain in the repository until the user explicitly deletes them.

IMAP is designed to manage remote mailboxes, as if they were local. Depending on the implementation of the IMAP client and the mail architecture required system manager, the user can save messages directly to client machine or store them on the server, or they are given a choice.

The POP protocol requires that a client connected to currently, was sole client connected to the mailbox. In contrast, IMAP allows simultaneous access by multiple clients and provides mechanisms for detecting changes made to a mailbox by other simultaneously connected clients.

When POP receives a message, it receives all of its parts, while the IMAP4 protocol allows clients to extract any of the MIME parts separately - for example, to obtain plain text without receiving attached files.

IMAP maintains flags on the server to keep track of the status of a message: for example, whether the message was read, whether a response was provided, or whether the email was deleted.

What are POP and IMAP and which one should you use for email?

If you've ever set up an email client or application, you've probably come across POP3, SMTP, and IMAP port conditions. Do you remember which one you chose and why? If you're not entirely sure what these terms mean and how each affects your email account, then the information below will shed some light on the matter. This article explains how POP and IMAP work and will help you decide which one best suits your needs.

The original protocol is POP. It was created in 1984 as a means to download emails from a remote server. IMAP was developed in 1986 to provide remote access To emails stored on a remote server. Essentially, the main difference between the two protocols is that POP downloads emails from a server for permanent local storage, while IMAP leaves them on the server and simply caches (temporarily stores) the emails locally. In other words, IMAP is a form of cloud storage.

Distinctive features of POP and IMAP?

These two protocols are best compared by looking at their core workflows.

POP workflow:

• connection to the server;
• receiving mail;
• local data storage;
• deleting correspondence from the server;
• shutdown.

The default behavior of POP is to delete mail from the server. However, most clients also provide the option to leave a copy of downloaded mail on the server.

Default POP3 ports:

• port 110 - unencrypted port;
• port 995 is an SSL/TLS port, also known as POP3S.

IMAP workflow:

• connection to the server;
• extraction of user-requested content and local caching (list of new emails, summaries of messages, or content of selected emails);
• treatment custom changes, for example, marking read letters, deleting data;
• shutdown.

As you can see, the IMAP workflow is a bit more complicated than POP. Essentially, folder structures and emails are stored on the server, and only copies are kept locally. Typically, these local copies are stored temporarily. However, permanent storage is available.

Default IMAP ports:

• port 143 - unencrypted port;
• port 993 is an SSL/TLS port, also known as IMAPS.

What are the benefits of POP?

As the original protocol, POP follows the simplistic idea that only one client needs to access mail on the server and that mail is best stored locally. This results in the following benefits:

• mail is stored locally, i.e. always available, even without an internet connection;
• Internet connection is only needed to send and receive mail;
• saves space on the server;
• the ability to leave a copy of the mail on the server.
• consolidation of multiple email accounts and servers into one mailbox.

What are the benefits of IMAP?

As mentioned in the introduction, IMAP was created to provide remote access to emails stored on a remote server. The idea was to allow multiple clients or users to manage the same mailbox. This way, no matter which device you use to log into your account, you will always see the same email and folder structures as they are stored on the server, and any changes you make to your local copies are immediately synced to the server.

As a result, IMAP has the following benefits:

• mail stored on a remote server is accessible from multiple locations;
• an Internet connection is required to access mail;
• more quick overview, because only the headers are loaded until the content is explicitly requested;
• mail is automatically reserved if the server is properly managed;
• saves local storage space;
• the ability to store mail locally.

What is the best email protocol?

The choice of protocol depends on your specific needs and current working situation. The following points should help you make your final decision.

Choose POP if:

• You only want to access your mail from one device.
• You need constant access to your e-mail, regardless of Internet availability.
• You have limited storage on the server.

Choose IMAP if:

• You want to access your email from multiple devices.
• You have a reliable and constant Internet connection.
• Do you want to receive short review new emails or emails on the server.
• Your local storage is limited.
• You are worried about the support of your emails.

If in doubt, please refer to IMAP. This is a more modern protocol that allows you to be flexible and your email is automatically backed up on the server. Plus, server space isn't usually an issue these days, and you'll still be able to store important emails locally.

Mail client errors

If you encounter POP3, Port: 995, Secure (SSL) error number 0x800C0133 when trying to check your Gmail, then try compressing your mail folders. In the POP client, choose File > Folder > Compress All Folders. This should fix the issue.

Currently, there are a lot of methods of communication via the Internet. You can use ICQ or Skype, social media, other resources. Approximately two decades ago the only way send or receive a virtual letter was an email.

Until a certain time, servers processing user letters had handicapped. Storing a large amount of information was expensive, which meant deleting the message from disk as soon as it was downloaded to the client's computer. Progress has gone forward, there are more opportunities, the user can store letters in the mailbox on the central server for an unlimited amount of time, and perform various operations with them.

Data transfer protocols used when working with e-mail

Any form of communication has a certain style - a set of agreements. On the web, it's a protocol. When working with E-mail, a number of protocols can be used. Among them:

• POP3;
• IMAP.

What is the difference, which protocol and in which case it is advisable to use?

What is POP3

Wanting to send a letter or check a personal mailbox located on a remote server, the user can use the browser installed on the computer, which is not very convenient. It is more often used, which exchanges information with the server using a specific protocol. If it is Post Office Protocol, the process is as follows:

1. Compound;
2. Receipt by the client of information about the state of the box, downloading letters;
3. Updating the server and deleting selected messages;
4. Closing the connection.

What is IMAP

The IMAP protocol provides the user with more possibilities. After authorization on the mail resource, only the headers of the letters are downloaded to the computer. When choosing desired message the client program downloads the letter completely. At the same time, you can work on-line and off-line. Read messages are not deleted, you can carry out the desired operations with them in the future.

Pros and cons of IMAP and POP3

Which protocol to choose? It all depends on the specifics of the job and needs.

In addition to the fact that letters are stored on the server without deletion, the advantages of IMAP include:

• Possibility of access to a box from several clients;
• Support for simultaneous access of multiple clients;
• Support for multiple boxes;
• Ability to create new folders that can be shared with other users;
• Ability to mark emails as read, important, and others;
• Server search support;
• Possibility of work in the mode of on-line.

Minus in this case the only one is that the user spends more time downloading letters from the central computer.

Which is better: POP3 or IMAP is not only 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 downloading to the mail client, or after a few days. This means that the letters are only in one place - either on the server or on the computer. If something happens to the computer, then you will run into a problem.

However, POP3 is still the most widely used email download protocol. The abbreviation "POP" stands for "Post Office Protocol". It works like a traditional post office. IMAP Difference from 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.

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

IMAP is more new 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. After that, your mail client downloads local copies of 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 whether you are going to work with e-mail from several devices or only one. If you read and send emails from your home and work computer, laptop, and tablet, then your best bet is to rely on the IMAP protocol.

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

IN modern world filled with all sorts of digital gadgets When choosing between POP3 and IMAP, it is better to give preference to the latest, newer protocol. With it, we break the hard link between the device, email client and email server. Now place and type operating system does not matter. And the reduction in the cost of data storage allows you to get at your disposal huge mailboxes. Today, only a few providers allow you to use e-mail only using the POP3 protocol. If you don't have any special reason to use POP3, choose the IMAP protocol.

As promised, I continue to publish descriptions of various network protocols. Since my last post was about the SMTP protocol, it is logical to continue the topic of email.

POP3 protocol (Post Office Protocol - version 3, the third version of the protocol post office) is the most common protocol for receiving email from a mail server. IMAP is also used for these purposes. IMAP has more features than POP3, but POP3 is much simpler. For comparison, POP3 is described in RFC1939, which is only 20 pages, and RFC3501, which describes IMAP, consists of as many as 108 pages. In this post we will talk about the POP3 protocol.

As always, let's start with the launch telnet utilities and a live example:

telnet mail.nic.ru 110
Trying 194.85.88.226...
Connected to mail.nic.ru.
Escape character is "^]".
+OK POP3 Server ready<[email protected]>
APOP [email protected]

Here we connect to a pop3 server, usually running on port 110, and authenticate (not to be confused with authorization). If the server greeting contains an e-mail-like line in triangle brackets (timestamp), then the server supports the APOP command, which allows you to send the password in encrypted (more precisely, hashed) form. In this example, the hash is calculated as follows:

echo -n "<[email protected]>qwerty" | md5

That is, the timestamp is concatenated with the password, and MD5 is calculated from the result. The advantage of this method is that even when using insecure connection an attacker will not be able to intercept the password. It will only see the hash, which will be completely useless, since the server uses a unique timestamp for each new connection. To find out the password, you need to crack the hash using brute force, which is practically useless for sufficiently strong passwords, which, moreover, change at least once every half a year.

The disadvantage of this method is that on the server side, passwords have to be stored in open form, otherwise how to check the correctness of the hash passed by the user? If an attacker gains access to the database, he will be able to steal all the passwords.

Therefore, most mail servers (I personally checked pop3.mail.ru:110 and pop.gmail.com:995/ssl/) do not support the APOP command and you have to authenticate using a standard login:password pair.

USER [email protected]
+OK please send the PASS
PASS qwerty
+OK 5 messages (868540 bytes) (proxing)

It is obviously preferable to use this method in conjunction with an encrypted connection than the APOP command. If authentication fails, we will receive a message like

So, authentication is passed, now you can run a few commands. Let's start with a few rather useless commands:

HELP
+OK Valid commands: QUIT, NOOP, STAT, LIST, UIDL, DELE, RSET, RETR, ...
NOOP
+OK cool
LAST
+OK 5 is last seen

The HELP command allows you to get a list of commands supported by the server. In this example, the UIDL, XTND, and XMIT commands are POP3 protocol extensions and the server is not required to support them. The UIDL command allows you to get unique message identifiers (see the description of the LIST command below):

UIDL
+OK 6 messages
1 3876
2 3877
3 3878
4 3879
5 3880
6 3881
.
UIDL 2
+OK 2 3877

I don’t know what XTND and XMIT are for, and it’s lazy to figure it out :) Those who wish can search for the answer in Google.

The NOOP command means "do nothing". Only one use of it comes to mind - to execute the command every 15 seconds to let the server know that the client has not hung.

The LAST command is obsolete and should not be used. It was once believed that an email client should pick up messages one by one. The LAST command was used to get the id of the last received message. It is currently supported by some servers solely for compatibility with older email clients.

Now let's move on to more useful commands:

STAT
+OK 5 868540
LIST
+OK 5 messages
1 275368
2 11196
3 153304
4 275367
5 153305
.
LIST 2
+OK 2 11196
TOP 2 0
+OK message follows
return path:
X-Blacklisted-By: cbl.abuseat.org
From: "=?koi8-r?B?48XO1NIg7cnH0sHDyck=?="
To: [email protected]
Subject: =?koi8-r?B?SGVsbG8=?=
Date: Thu, 17 Dec 2009 18:18:12 +0300
MIME Version: 1.0
Content-Type: multipart/related;
type="multipart/alternative";
boundary="----=_NextPart_000_003C_01CA7F45.01CA7F45"
X Priority: 3
X-MSMail-Priority: Normal
Xmailer: Microsoft Outlook Express 6.00.3790.3959
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4325
Received-SPF: none
X-Spam-Rating: 83.69

.
DELE 2
+OK marked deleted

The STAT command allows you to determine the number of messages in the mailbox (5) and their total size (868,540 bytes).

The LIST command shows us a list of message IDs and their size in bytes. The list ends with a dot. As an argument to this command, you can pass the id of the message, then in response we will receive the size of only this message.

The TOP command allows you to get the message header (the first command argument is the message id) and the first N lines of the message body (the second command argument). In this example, I specified N=0 because I only wanted to see the title of the message. You might as well have just given only one argument. The server response also ends with a dot. The TOP command is often used by email clients to determine the sender and subject of a message without having to download the entire email. This saves time and traffic for the user.

Obviously, we are dealing with spam here (see sender's e-mail, X-Blacklisted-By and X-Spam-Rating), so you can safely delete the message without even downloading it in its entirety. For this, the DELE command is used. The message will be marked for deletion, but only deleted after we close the connection.

You can cancel the deletion of all messages marked by us with the command RSET. You can get the whole message with the command RETR . As with TOP, the end of the message is indicated by a dot. I will not give examples of these commands, since everything is pretty obvious here.

At the end of the work, you can say goodbye to the server and close the connection:

QUIT
+OK CommuniGate Pro POP3 Server connection closed

That's probably all I wanted to talk about the POP3 protocol. I hope this description will be useful for you. If you have questions or find an error in the text, write in the comments, do not be shy.

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

What is POP3?

Protocol version 3 (POP3) is the standard mail protocol The used to receive email from the remote server to the local email client. Allows you to download messages to your local computer and read them even if the user is in offline. Please note that when using the POP3 protocol 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 securely connect to POP3.

What is IMAP?

Internet Message Access Protocol (IMAP) is an email retrieval protocol used to access it 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 assumes that your email address is accessible only from one application, while IMAP allows you to log in from multiple clients at the same time. That's why IMAP fit better if you intend to access your email from multiple locations, or if your messages are managed by multiple users.

The IMAP protocol runs on two ports:

port 143 is unencrypted IMAP port default;

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

What is SMTP?

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

SMTP works 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 for e-mail exchange? Concepts and terms

The term "email server" refers to the two servers needed 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. Access to incoming messages requires 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 can use a dedicated mail client (for example, Outlook Express) or web browser. So, Internet Explorer used to access email-based accounts. Letters are stored on the incoming mail server until they are downloaded. Once you have downloaded your mail from the mail server, you will not be able to do it again. To successfully upload data, you must enter correct settings in electronic mail program. Most incoming mail servers use one of the following protocols: IMAP, POP3, HTTP.

Outgoing mail server (SMTP)

This is the server used only for sending emails (for transferring them from your mailbox). client program to the receiver). Most outgoing mail servers use Protocol to send mail. 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 which will allow you to send emails from any account. Due to spam issues, most outgoing mail servers won't let you send emails unless you're logged into your network. An open relay server will allow you to use it to send emails, whether or not you belong to it network group or not.

Email Ports

For networks, port means end point logical connection. The port number determines its type. The default email ports are listed below:

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, the protocol is standard method used at each end of the link. To deal with email, you must use a special client to access 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 the data is stored by your Internet server. Because it only requires a small amount of data transfer, it works well even on a slow connection, such as a dial-up connection. When trying to read specific message The email client downloads data from the server. You can also create and manage folders or mailboxes on the server, delete messages.

POP3 protocol

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

When using the POP protocol, all your email messages will be downloaded from the mail server to the local computer. You can also leave copies of your emails on the server. The advantage is that once your messages have been downloaded, you can turn off your internet connection and read your e-mail at your leisure without resorting to additional costs for communication. On the other hand, with this protocol, you receive and download a lot of spam messages(including spam or viruses).

SMTP protocol

Protocol used by the Mail Transfer Agent (MTA) for delivery 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 use the SMTP protocol under certain conditions.

HTTP protocols

HTTP is not a protocol designed for email communication, but it can be used to access your mailbox. It is also often referred to as web email. It can be used to compose or receive emails from your account. hotmail- good example HTTP usage as an email protocol.

Managed File Transfers and Networking Solutions

Your ability to send and receive email is mainly 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 protocol, or Simple Mail Transfer Protocol, mainly used to send email from mail client(for example, Microsoft Outlook, Thunderbird or Apple Mail) to the 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 deprecated. But in fact, it is still used by several mail service providers.

POP3

The Post Office Protocol, or POP, is used to retrieve email messages from 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 attackers from gaining access to user messages.

The POP3 client receives the email like this:

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 so that the server can continue to store copies of downloaded messages, the above steps are common practice.

IMAP

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

Operation logic (imap4 settings):

• connects to the mail server on 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. The IMAP specifications can be found in RFC 3501.



Choosing between IMAP and POP3

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

If storage space on the server is important to you, then choose POP3. A server with limited memory is one of the main factors that can 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's better to stick with IMAP. There is one good reason why IMAP was designed to store messages on the server. It is used to search for messages from multiple devices - sometimes even at the same time. So if you have an iPhone, android tablet, laptop and desktop and you want to read email from any or all of these devices, then IMAP is your best bet.

Synchronization is another benefit of IMAP. If you're accessing email messages from multiple devices, you'll likely want them all to show whatever actions you've taken.

For example, if you're reading messages A, B, and C, you want them to be marked as "read" on other devices as well. If you have deleted letters B and C, you will want the same messages to be deleted from your mailbox on all gadgets. All of these synchronizations can only be achieved if you use IMAP.

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

Of course, everything functionality IMAPs come with a price. These solutions are harder to implement and end up consuming a lot more CPU and RAM, especially when it's doing the synchronization process. Actually high loading cpu and memory can happen both client side 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 depend heavily on end users. They would generally prefer to download all email messages and not leave a copy of it on an unknown server.

Speed ​​is an advantage that varies and depends on the situation. POP3 has the ability to download everything mail messages when connected. And IMAP can, if necessary (for example, when there is not enough 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 advantages and disadvantages. It's up to you to decide which features or capabilities are more important.

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

However, users who exchange mailboxes or access their emails with different computers, will prefer IMAP.

Spam firewalls with SMTP, IMAP and POP3

Most spam firewalls only deal with SMTP protocol and protect him. Servers send and receive email SMTP mail, and they 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. For example, Exchange or Dominos must configure proxy-based message routing to the firewall when sending email, and also provide the ability to send email from the firewall.