The incoming mail server settings are incorrect. What is POP3, SMTP and IMAP

28.06.2019 Operating Systems

Chances are, most of you reading this guide are already familiar with the most commonly used communication technology, email. But have you ever wondered how it actually works? In this article, we will learn how this service works and what is POP3, SMTP and IMAP.

POP3(Post Office protocol version 3) is often used to communicate with a remote email server and download messages to a local email client and then delete it on the server, e.g. Thunderbird, Windows Mail, etc. However, usually email clients offer a choice - whether or not to leave copies of messages on the server. If you use multiple devices to send messages, it is recommended to leave this feature enabled, otherwise you will not be able to access sent messages on another device that have not been saved on a remote server. It's also worth noting that POP3 is a one-way protocol, which means that data is taken from a remote server and sent to a local client.

The default POP3 ports are:

Port 110 - non-encrypted port

Port 995 is the SSL/TLS port, also known as POP3S

Step 2 - Differences between POP3 and IMAP, and what ports does IMAP have?

IMAP (application layer protocol for accessing email), as well as POP3, is used to receive email messages on a local client, however, it has a significant difference - only the headers of email messages are downloaded, the body of the letter itself remains on the server. This communication protocol works in two directions, if changes occur on the local client, they are transmitted to the server. Recently, IMAP has become more popular as email giants like Gmail recommend using it instead of POP3.

The default IMAP ports are:

Port 143 - non-encrypted port
Port 993 is the SSL/TLS port, also known as IMAPS

Step 3 - SMTP, the protocol for outgoing email communications

Simple Mail Transfer Protocol ( SMTP) is used to communicate with a remote server and then send messages from the local client to the remote server, and ultimately to the recipient's server. On your email server, this process is controlled by a special service ( MTA). It is worth mentioning that SMTP is used exclusively for sending messages.

SMTP Ports:

Port 25 - non-encrypted port
Port 465 is the SSL/TLS port, also known as SMTPS

Conclusion

We hope that you now have a clear understanding of how mail protocols work and what ports they use. In this guide, we learned what POP3, SMTP and IMAP are and what they are used for. For example, POP3 and IMAP are used for the same purposes, but they approach these tasks in different ways. IMAP leaves the contents of the email on the server, while POP3 downloads it to your computer. Also, we learned what standard ports SMTP, POP3 and IMAP have.

Yandex mail settings for client mail clients:

IMAP setup:

Using the IMAP protocol, the mail program will not only download new letters, but will synchronize the information on your computer with the data on the server, displaying the entire structure of your mailbox at once - all folders, both standard and manually configured by you.

To configure an email client using the IMAP protocol, specify the following data:

in the section Incoming messages / Incoming mail (IMAP) you need to specify the address of the mail server imap.yandex.ru, install SSL protection and port 993 port 143 and connect without SSL in the Outgoing mail (SMTP) section, you must specify the server address smtp.yandex.ru, and connect via a secure SSL connection through port 465. If you cannot use a secure connection, you can connect to SMTP -server by ports 25 or 587

When configuring email programs, you must specify your Yandex username and password as the login and password for accessing the mail server. As a login, you must specify the full address of the mailbox.

Support for the IMAP protocol will be enabled automatically upon first authorization in the mail program. You can also enable IMAP protocol support yourself in the Settings ("Mail Clients" section)

Enabling IMAP may take some time.

After successful activation, the checkmark will become inactive, and the inscription will change to "IMAP enabled". It will be impossible to disable IMAP support for your mailbox, you can simply not use this protocol.

POP3 protocol setting:

When using the POP3 protocol, all your letters (from those folders that you specify in the mailbox settings) will be downloaded by the mail program to your computer in the Inbox folder, after which they can be sorted into folders, if necessary, using filters configured in the mail program itself .

To save emails in a mailbox, you can set the option to save copies of emails on the server when downloading in the mail program settings, if your program allows you to do this. It is not possible to make this setting on our side.

When setting up a mail program using the POP3 protocol, you must specify the following data:

in the section Incoming messages / Incoming mail (POP3) you need to specify the address of the pop.yandex.ru mail server, install SSL protection and port 995. If for some reason your program does not support SSL connection protection, you can specify port 110 and connect without SSL in the Outgoing mail (SMTP) section, you must specify the server address smtp.yandex.ru, and connect via a secure SSL connection via port 465. In case you cannot use a secure connection, you can connect to the SMTP server using ports 25 or 587

When configuring email programs, you must specify your Yandex username and password as the login and password for accessing the mail server. In case you configure access to a box of the form [email protected], the login is the first part of the address - login. If you use Yandex.Mail for Domains, you must specify the full mailbox address as a login.

If you download mail using a mail client using the POP3 protocol, you can:

Leave all default settings. Then only letters from the Inbox folder will be downloaded. Set up downloading emails from any set of folders, including the Spam folder or your own folders. You can select folders for downloading on the "Settings" page - in the "Mail clients" section. You can also set the setting "When receiving mail via POP3, mark letters in the Yandex.Mail mailbox as read", which already in the web interface will allow you to understand which letters were picked up by the mail client. When clients download mail, emails are not marked as read by default.

Most email service users are quite happy with the standard web client that their service provider offers them. Actually, it is in this form that this mail service is used most often, but this is not because it is so convenient, but because people simply do not know where to find an alternative and how to configure mail reception in third-party programs . If email is your work tool, then you probably won't be able to do without an advanced email client that would replace the web interface. In this article, we will analyze how to create a mailbox on the Mail.ru domain and implement (IMAP) for various client programs, including Outlook and Apple Mail. Here we will analyze the main errors that arise when working with the mail service in general and with third-party mail clients in particular.

Box Registration

You can register Mail.ru on the official website of the service.

When registering, you must fill in a number of mandatory fields with personal data:

Name - you can specify any, despite the requirement to enter a real name.
Surname - you can specify any.
Mailbox - you must specify a nickname, but the mail will offer it itself.
Password - you must specify a complex password using special characters.

There are other fields, but they are optional.

IMAP protocol

This protocol is the most optimal and convenient for working with e-mail and is supported by all popular mail services. In addition, storing mail in the cloud has a positive effect on security and reliability (letters will definitely not be lost and will always be available on different devices).

Proper configuration of Mail.ru via the IMAP protocol requires knowledge of certain data to provide access to the mailbox:

The email address (box name/email adress) is the full name of your mailbox, followed by the @ dog icon and the domain name.
Next, you should designate the server for incoming IMAP mail - in our case, imap.mail.ru.
sent from the SMTP server - in our case, the smtp.mail.ru server is installed
Password - the password currently used (to access the mailbox).
Then you should enter the port for the IMAP server (we select port 993, and as the encryption protocol SSL / TSL).

Outlook

Setting up Mail.ru (IMAP) for a Microsoft client varies depending on which version you are using. In the 2016 version you need:

Go to the "File" menu in the top left corner.
Then go to the "Details" submenu.
Then click "Add account".
You will be prompted to select one of the tuning modes (manual or automatic), you must select manual and specify all the data described above.
Username, mailbox address, current password.
Next, you need to select the type of IMAP account and specify the appropriate servers.
Then you should open "Advanced Settings".
Select the "Advanced" submenu and enter port 993 in the IMAP server field.

The Bat!

Setting up Mail.ru (IMAP) in this client is carried out using the built-in utility interface, which offers step-by-step data entry.

You need to add a new box, to do this, you need:

In the upper panel of the interface, click on the "Box" button and select the "New mailbox" submenu.
Specify any name of your choice, for example "Working mail".
On the next settings screen, you need to enter your full name, email address, and organization.
On the next settings screen, you need to specify the IMAP server data - imap.mail.ru.
On the final settings screen, you must enter your email address and password to enter it.

For further configuration, you need to go to "Mailbox Properties" and specify the IMAP port 993, and the SMTP port 465.

Apple Mail

Setting up Mail.ru (IMAP) in the macOS system is carried out at the level of system settings, or through the built-in Mail program.

To configure through the Mail application, you must do the following:

Open the Mail app itself.
Select "File" from the top menu.
Select the "Add account" submenu.

Just like in the case of The Bat, Apple's client offers step-by-step configuration.

In the first window, you will be prompted to enter the basic data for the box:

Your name (any name of your choice, it should not be associated with a mailbox).
Email address (full address with @ and domain).
Password (used when registering on the mail.ru website).

The program will make further settings automatically, but errors may occur, and then the program will prompt you to enter additional data.

Server type - select IMAP.
Description - the name of the mailbox (any, at the user's choice).
The server where incoming mail will be received is imap.mail.ru.
Password - the password used when registering on the mail.ru website.

The server where your letters will be sent from - you need to specify the server smtp.mail.ru (attention, you must also check the box next to the option "Use only this server", as well as opposite the option "Use authentication").
Username - here you need to enter the full email address, along with @ and domain.
Password - the same password that was entered in the previous window.

After the performed operations, the program will offer to check all the data again and create a new box.

After a new mailbox has been added to the list of mailboxes in the program, you need to change the port in the settings. For this you need:

Open Mail preferences.
Select the "Accounts" submenu.
In this submenu, you need to find the item "Outgoing mail server" and select the sub-item "Change the list of SMTP servers" in the drop-down menu.
Next, you need to check the box next to the option “Use an arbitrary port” and enter port 465 there.
Next, you need to check the box next to the "Use SSL" option.

Mail for iOS

Setting up Mail.ru (IMAP) in iOS is done in the same way as in macOS, through the system settings. To add a new mailbox:

Go to "Settings - Mail".
Open the list of accounts and click on the "Add account" button.
Select "Other" from the list of suggested domains.
Next, you need to specify the basic user data (name, email address, password).
Then you should click on the "Next" button, and the program will complete the setup itself.

You will have to specify the server and ports manually, for this you should:

Click on the name of the newly created mailbox.
Open mailbox settings.
In the SMTP item, you must specify smtp.mail.ru.
In the IMAP item, you must specify imap.mail.ru.
In the SMTP settings, you must check the box next to the "Use SSL" option and enter port 465.

Mail for Android

To begin with, it is worth deciding which mail client is installed in the system. This guide provides instructions for setting up a standard client for Android. Mail.ru (IMAP) is configured manually. To add a new mailbox:

Open the Email application.
Enter your mailbox details (full address with @ with domain and password used during registration).
Then tap the Manual key.

Select an IMAP server type.

An additional menu will appear, in which you will need to enter data for the server with incoming mail:

IMAP server - imap.mail.ru.
The security protocol is SSL/TSL.
You must also change the port to 993 and click Next.

An additional menu will appear where you will need to enter the data of the server with outgoing mail:

SMTP server - smtp.mail.ru.
The security protocol is SSL/TSL.
You should also enter the port number 465 and click the "Finish" button.

Official client

In order not to bother with setting up Mail.ru (IMAP) for third-party clients, you can download the official application, which is available for download from all major application stores, including the AppStore and Google Play. An important advantage of these applications is that there is no need to enter server data manually. All you need to know is the password (the one that was used during registration) and the email address (the application will automatically substitute the domain). Moreover, the registration process itself can be completed in a mobile application without resorting to using the website. The application interface is pre-designed for maximum convenience for those who use mail.ru mail. If the user has boxes in other services, then you can add them directly to the same application, and all correspondence will come to one program. As for desktop computers and laptops, then, alas, the developers have nothing to offer, except for the web client.

Possible mistakes

As with any email service, and software in general, problems can arise. The same applies to Mail.ru (IMAP) settings for third-party email clients.

Error 550 Message sending for this account is disabled (Sending messages for this account is prohibited) - the problem is solved by changing the password for the mailbox.
Mailbox Full Error - From the name it is clear that the problem arose due to the fact that the mailbox is full. You need to wait a while or clear your inbox.
Error User not found (User not found) - a similar error appears if the addressee is not registered in the Mail.ru database. In this case, you need to double-check the recipient's address or another way to contact him.
Error No such message, only 1000 messages in maildrop (There is no such message, only 1000 messages in mail) - an error occurs when trying to load correspondence into a third-party mail client. To fix it, you need to open your email inbox through a web browser and delete the oldest letter from it, and then try to upload them again using a third-party email client.
Error We do not accept mail from dynamic IP (We do not accept letters from mailboxes with a dynamic IP address) - the problem occurs due to an incorrectly configured PTR (it looks like an entry for dynamic IP addresses). Because of the dominance of spam, Mail.ru management had to block such addresses. Only a provider that will change the PTR can fix the problem.
Error 550 Spam message discarded/rejected - This error means that the email was blocked by a spam filter. The problem can only be solved by the support service.
Error Access to this account is disabled (Access to the account is closed) - most likely, the box to which you are trying to send an email has been deleted, as it has not been used for a long time.

If you want to receive mail using your mail clients, enable POP3 or IMAP protocols.

To do this, go to the Settings of your mailbox on Yandex, open the " Mail programs". Select the protocol you want to use by ticking its box. Save the result by clicking the "Save Changes" button.

Read more about POP3 and IMAP protocols below.

IMAP setup

To set up an email client using the IMAP protocol, specify the following data:

In chapter Incoming mail/Incoming mail (IMAP) you need to specify the address of the imap.yandex.ru mail server, set SSL protection and port 993. If for some reason your program does not support SSL connection protection, you can specify port 143 and connect without SSL
In chapter

Support for the IMAP protocol will be enabled automatically upon first authorization in the mail program.

POP3 setup

When using the POP3 protocol, all your letters (from those folders that you specify in the Mailbox Settings) will be downloaded by the mail program to your computer in the Inbox folder, after which they can be sorted into folders, if necessary, using the filters configured in the mailbox itself. program.

Keep in mind that many email programs delete emails from the server by default when downloading. In this case, all letters in your mailbox will be moved to the "Deleted Items" folder, from where they will be deleted after a week. To save emails in a mailbox, you can set the option to save copies of emails on the server when downloading in the mail program settings, if your program allows you to do this. It is not possible to make this setting on our side.

When setting up a mail program using the POP3 protocol, you must specify the following data:

In chapter Incoming mail/Incoming mail (POP3) you need to specify the address of the pop.yandex.ru mail server, set SSL protection and port 995. If for some reason your program does not support SSL connection protection, you can specify port 110 and connect without SSL
In chapter Outgoing mail (SMTP) you must specify the server address smtp.yandex.ru, and connect via a secure SSL connection on port 465. If you cannot use a secure connection, you can connect to the SMTP server on ports 25 or 587

(SMTP) is the standard for e-mail. Originally fixed in RFC 821 (1982), last updated in 2008 with extended additions to SMTP by RFC 5321 (a widely used protocol today).

Although mail servers and other mail agents use SMTP to send and receive e-mail, custom class software typically uses SMTP ports only to send data to the server for relaying. Client applications typically use either IMAP or POP3 to receive messages. These protocols are the most convenient and in demand for these purposes: they have extended functionality and a wide range of capabilities.

Characteristics

SMTP communication between mail servers uses TCP port 25. Mail clients often send outgoing mail to the mail server on port 587. Even though legacy mail providers still allow the non-standard port 465 to be used for this purpose.

TLS-secured SMTP connections, known as SMTPS, can be made using the STARTTLS technology.

Proprietary and email systems use their own non-standard protocols to access mailboxes on their mail servers - all companies use SMTP server ports when email is sent or received outside of their own systems.

Destination SMTP

Nearly all activities on the Internet are made possible by protocols—special network software rules that allow a computer to communicate with all networks so that users can shop, read the news, and send e-mail. Protocols are vital to day-to-day network activity—they are built into network software and used by default.

The SMTP Port Protocol provides a set of codes that facilitate the exchange of email messages between servers (the network computer that handles incoming and outgoing email). This is a kind of shorthand that allows the server to break down the different parts of the message into categories that another server can understand. When a user sends a message, it turns into lines of text separated by code words (or numbers) that define the purpose of each section.

Technical terminology

SMTP is a TCP/IP protocol used for e-mail. However, since it is limited to being able to send messages to a queue on the receiving end, it is usually used with either POP3 or IMAP, which allow data to be stored on the server and downloaded as needed. In other words, it is common to use an application that chooses SMTP for sending e-mail and POP3 or IMAP for receiving correspondence. On Unix-based systems, sendmail is the most widely used SMTP server for email. The commercial Sendmail package includes a POP3 server. Microsoft Exchange includes an SMTP server and can also be configured to support POP3.

SMTP is typically used to work over Internet port 25. An alternative to SMTP, which is widely used in Europe, is X.400. Many mail servers now support the Extended Simple Mail Transfer Protocol (ESMTP), which allows you to transfer media files as email.

Story

In the 1960s, various forms of electronic messaging were used. Users communicated using systems built for specific mainframes. As more and more computers became interconnected, there was a need to develop standards to allow users of different systems to send e-mail to each other. SMTP originated from these standards developed in the 1970s.

Further implementations include the FTP Mail Protocol starting in 1973. Development work continued into the 1970s until ARPANET transitioned to the modern Internet in 1980. Then Jon Postel proposed a mail data transfer protocol.

SMTP became widely used in the early 1980s. At the time, this protocol was a Unix add-on for the Unix Copy Program mail program. SMTP works best when both the sending and receiving machines are connected to the Web, use a store and send mechanism, and are examples of push technology.

Mail processing model

E-mail is sent by an email client (Mail User Agent, MUA) to a mail server (Mail Submission Agent, MSA) using SMTP on TCP port 587. Most mailbox providers still allow sending on the traditional port 25. MSA delivers mail to your mail agent (mail transfer agent, MTA). Often, these agents are instances of common software activated with different settings on the same computer. Local processing can either be done on a single machine or shared across multiple machines. Mail agent processes on the same machine can exchange files, but if processing is done on multiple machines, they relay messages between each other using an SMTP port where each machine is configured to use the next machine as a smart host.

Protocol Overview

SMTP is a text-based, connection-oriented protocol in which a mail sender communicates with a mail recipient by issuing command lines and providing the necessary data over a reliable, ordered data flow channel. An SMTP session consists of commands issued by the SMTP client (originating agent, sender, or transmitter) and corresponding responses from the SMTP server (listening agent, or recipient). A session can include zero or more SMTP transactions, which consist of three command/response sequences:

In addition to the intermediate response for DATA, each server's response can be either positive or negative (code 2xx). Negative responses can be permanent (5xx codes) or temporary (4xx codes). A reject is a permanent failure, and the client must send a reject message to the server it received it from. A fall is a positive response followed by a rejection of the message.

SMTP mail ports and their meaning

SMTP is a delivery protocol only. In normal usage, mail is sent to a target mail server, such as the SMTP server on the mail port. Data is routed based on the destination server, not the individual users it is addressed to. Other protocols (POP or IMAP) are specifically designed for use by individual users who receive messages and manage mailboxes. SMTP, POP, and IMAP are not acceptable mail relay protocols for computers with intermittent connectivity. They are designed to work after final delivery, when information critical to the correct operation of the mail relay has been removed.

Start the empty message queue

Remote Message Queue Starting is an SMTP feature that allows a remote host to start mail processing on the server so that it can receive messages meant for it by sending the TURN command. However, this feature posed a potential data security risk and was extended in RFC 1985 by the ETRN command, which works more securely using the Domain Name System information-based authentication method.

International email address

Users whose script is not Latin, or who use diacritics not in the ASCII character set, had difficulty requiring a Latin-script email address (mail.ru SMTP port). RFC 6531 was created to address this issue by providing internationalization capabilities for SMTP, the SMTPUTF8 extension, and support for multibyte and non-ASCII characters in email addresses. Examples: diacritics and other language symbols (Greek and Chinese). Also relevant for the Yandex SMTP port.

Current support for this document is limited at the moment, but there is strong interest in the widespread adoption of RFC 6531 and related RFCs in countries such as China that have a large user base where Latin (ASCII) is the foreign script.

Outgoing mail SMTP server

The email client must know the IP address of its source SMTP server. This must be specified as part of its configuration (usually a DNS name). This server will provide outgoing messages on behalf of the user.

Outgoing mail server access restrictions

Server administrators need to impose some control on which clients can use the server. This helps fight abuse and spam. The following solutions have been widely used:

in the past, many systems have imposed restrictions on the use of a client's location, only allowing use by clients whose IP address is one of the server's administrators. Use from any other client IP address is prohibited.

Modern SMTP servers usually offer an alternative system that requires clients to authenticate with credentials before allowing access.

SMTP - what port is used?

Communication between mail servers usually always uses the default TCP port 25 assigned for SMTP. However, mail clients usually use specific smtp ssl port ports instead. Most ISPs now block all outgoing port traffic from their customers as a spam protection measure. For the same reason, businesses typically configure their firewall to allow outbound port from designated mail servers.

SMTP transport example

A typical example of sending a message via SMTP to two mailboxes (alice and theboss) located in the same mail domain (example.com or localhost.com) is reproduced in the following exchange session. After the message sender (SMTP client) establishes a reliable communication channel for the message receiver (SMTP server), a session is opened with the server, usually containing its fully qualified domain name (FQDN), in this case smtp, example, or com. The client initiates its dialog box by responding with a HELO command identifying itself in the command parameter with its fully qualified domain name (or address literal if not available).

Additional extensions

Clients find out which options the server supports by using the EHLO greeting instead of the original HELO. Clients are only returned to HELO if the server does not support the SMTP extensions.

Modern clients can use the ESMTP extension's SSRE keyword to query the server for the maximum message size that will be accepted. Legacy clients and servers may attempt to send oversized messages that will be rejected after using up network resources, including connection time to network links.

Spam protection methods and email authentication

The original design of SMTP had no way to identify senders or check if servers were allowed to send on their behalf. As a result, email spoofing is possible, which is commonly used in email spam and phishing.

Special offers are being made to change SMTP or replace it entirely. One example of this is Internet Mail 2000, but neither it nor any other has had much success in front of the network effect of the huge installed base of classic SMTP. Instead, mail servers now use a range of methods, including DomainKeys, DomainKeys Identified Mail, Policy Policy Framework and DMARC, DNSBLs, and greylisting to reject or quarantine suspicious emails.