0 votes
please explain with some examples


asked May 28, 2015 in Computer Science - IT by macIN | 134 views

2 Answers

+2 votes
Selected Ans.

SMTP  - Simple Mail Transfer protocol 

It is a text based protocol . Here we can specify one or more  recipients of a message along with the message and encoded objects .

               transferred to 

Message   -------------------> remote server.

 Then the communication between the  client and the server takes place.

SMTP uses port 25

where as 


POP is a very simple protocol that only allows downloading of messages from your Inbox to your local computer. Generally, once transferred, the email is then on your local computer.

we normally use POP3 

.POP3 uses port 110. 


IMAP - Internet Message Access Protocol


It is a much more advanced protocol that allows you to see all your folders to quickly view subjects and message bodies of emails.  But  on downloading a larger email it delays its speed. IMAP also allows you to synchronise mail folders on the web, so that you see the same folders and messages wherever and however you access your email.


 IMAP uses port 143.  

Like gmail drive that saves your pictures and files . So that yu can access and download whenever you want 



Why above protocols use different ports?is there any significance in that ? Also i assume that SMTP is used in gmail ,SMTP is text based protocol.what do that denote "text based"? So i cannot send other things than text like images ?

 The above protocols uses different port Since, For networks, a port means an endpoint to a logical connection. The port number identifies what type of port it is. So we have dedicated port  number for each of this

If it is SMTP : Then we use port number 25 for SENDING EMAILS.

It is the standard protocol for sending emails across the Internet.

And SMTP is used to send only text email . Since there were a problem with binary files  like IMAGES , standards such as 

MIME came into picture (Multipurpose Internet Mail Extensions ) were developed to allow binary files to be encoded and sent via SMTP.


If it is for POP3 ::: Then we use port number 110 which is a dedicated port to  receive emails from a remote server to a local email client. The main disadvantage of POP3 is when you use POP3 to connect to your email account, messages are downloaded locally and removed from the servers.

If it is IMAP  :::: Then we use port number 143  for retrieving emails . 

Here you may have the doubt that both POP3 and IMAP  are used for the same purpose. Yup exactly it is .

While the POP3 protocol assumes that your email is being accessed only from one application, IMAP allows simultaneous access by multiple clients. This is why IMAP is more suitable for you if you're going to access your email from different locations or if your messages are managed by multiple users.


answered Jun 18, 2015 by nagini s
selected Jun 20, 2015 by macIN
@nagini  ,Why above protocols use different ports?is there any significance in that ? Also i assume that SMTP is used in gmail ,SMTP is text based protocol.what do that denote "text based"? So i cannot send other things than text like images ?
+3 votes

SMTP, POP3 and IMAP are TCP/IP protocols used for mail delivery.

  • Simple Message Transfer Protocol – SMTP
  • Internet Message Access Protocol – IMAP
  • Post Office Protocol version 3 – POP3

What SMTP does is allow you to send out a message to your Internet server and from there route around to it’s final destination. Once it arrives at it’s final destination, it’s stored on that mail server until an e-mail client grabs it.


POP3 is excellent if all you want to do is pull down mail from the server to a single client. This could be a single desktop computer (perhaps using Outlook or Thunderbird or any other desktop e-mail client).  


What’s nice with IMAP is that it synchronizes with two or more applications (whether on one computer or several devices).  So, if you have a blackberry or an iPhone or several computers or all of the above and you want to be able to read the same messages from each e-mail client, then IMAP is the system for you.



In order for two computers or devices on the Internet to communicate they have to follow a set of communication rules, this is called a protocol, most things on the Internet use the TCP/IP set or stack of protocols.

Each of these protocols is assigned a unique port number to communicate over so that the computers always know exactly what protocol they need to use, to communicate.Some commonly used protocols are:

  • HTTP - used for websites and uses port 80
  • DNS - used for resolving Internet domain names to IP addresses and uses port 53
  • FTP - used for transferring files across the Internet and uses port 21
  • POP3 - used for collecting email and uses port 110
  • IMAP - also used for collecting email and uses port 143

What is port 25 ?

Port 25 is the default port used to transport or communicate email across the Internet using the SMTP protocol.

You can use any port, really. Port 25 is a convention, that's all. I hear that some providers block port 25 for outgoing traffic (to reign in spam bots), and people have to switch to other ports.


answered Jun 19, 2015 by jiya