POP3, IMAP, and SMTP EMAIL Protocols.

  • Sotware

In this world, we are very well accustomed to the term Email. Every business is now dependent on mail communication and every Desktop, laptop, and tablet has an Email app installed on it. Emails have brought the world so close that in a minute we can send or receive a document from one part of the world to another. When Email is sent by a sender it is transmitted to an Email server and then it is received by the receiver. All this is possible due to protocols. One protocol is used to send mail and another one to receive mail. We will explain the three most commonly used protocols and for what specific reasons they are used. Three commonly used protocols are POP3, IMAP, and SMTP. Firstly we will describe all three protocols one by one

POP3-Post office Protocol.

POP3– Post office protocol is the protocol used for receiving messages from the email servers to mail clients. The version widely used for this protocol is version”3” and so this protocol is called POP3. This protocol connects to the Email server and downloads the mail to the receiver client. As the mail is downloaded you can also read mail when you are offline. After downloading as per common settings email is deleted from the mail server. This means is you are using mails form different locations POP3 is not a proper option are we can also select the option to keep a mail copy on the server.

By default the POP3 protocol works on the following  two ports

Port 110 – This port is default POP3 non-encrypted port

Port 995 – This is secured SSL/TLS POP3 port.

POP3 conducts following four steps while retrieving a mail from server.

  • 1. Connect  to the mail server on port 110 or 995 for SSL/TLS connections;
  • 2. Retrieves email messages sent by the sender; 
  • 3. Deletes copy of the mail  the server;
  • 4. Disconnects from the server

IMAP- Internet message access protocol

Internet Message Access Protocol (IMAP) is a protocol to receive or access emails stored on the server similar to POP3. The fourth version is in use, as a result, this protocol is called as IMAP4. The main feature of this protocol is that when the message is retrieved from the mail server a copy of the message remains on the server. As a copy remains on the server it can be accessed from any location and any authorized device. IMAP is a protocol used for multiple clients. As the protocol allows reading the message from any location the messages are always synchronized well-sorted and classified.

IMAP uses two ports for retrieving mails

Port 143 – This port is default POP3 non-encrypted port

Port 993 – This is secured SSL/TLS  IMAP port.

IMAP conducts following four steps while retrieving a mail from server.

  • 1. Connect  to the mail server on port 143 or 993 for SSL/TLS connections;
  • 2. Retrieves email messages sent by the sender; 
  • 3. Remains connected to the server and download messages as per user demand until mail client disconnects connections.

Here one thing happens that mail is not deleted from the server and therefore is IMAP is the widely used protocol.

SMTP- Simple Mail Transfer Protocol.

Simple Mail Transfer Protocol (SMTP) is the protocol for sending emails to the mail server. This protocol is also used to transfer mails between mail servers. The relay of mails from one server to another server is necessary if the sender and recipient have different email services. 

SMTP uses following three ports for sending mails

Port 25 – This port is default SMTP non-encrypted port.

Port-2525 – Mail server also supports 2525 for sending non-encrypted mails, which is another alternative port for port 25.

Port 465 – This mail protocol is secured port used to send the mail.

Three main steps while sending mail with SMTP is as follows

1. The SMTP client connects with a TCP connection to the SMTP server. After that Once the connection is established the server confirms the recipient’s address.

2. When the recipients address is confirmed the transfer of the email starts. And the message is transferred. 

3. After transfer of mail Client and mail server is disconnected using QUIT command

Mail Transfer process 

Now to sum up we know and have learned how POP3, IMAP, and SMTP protocol works separately, let’s see the process how a mail sent by a sender is transferred  the recipient

1. The mail sender (email client) connects to the SMTP server.

2. The STMP protocol confirms the recipients email address authorizes the recipient; it sends the email to the SMTP server of recipient.

3. Recipient mail client verifies the account and SMTP server forwards the email to the IMAP/POP3 server.

4. The mail is accessed or downloaded by receivers email client.

In short this is the process of mail transfer.

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