SMTP – The Working Agent to Send And Receive Emails

One of the most valuable emerging services found on the internet today is said to be Email. From one user to another user an Email is transferred using a simple mail transfer protocol (SMTP) process and this process is merely a push protocol to send an Email. Like SMTP there are also other two important protocols such as post office protocol or internet message access protocol which is commonly used for retrieving the mails at the side of the receiver. 

General fundamentals of SMTP 

This SMTP is simply an application layer protocol and the client who is in need of sending mail must open a TCP connection towards the SMTP server and then the client’s mail is send across the connection. This server SMTP will always remain on the listening mode and when this simple mail transfer protocol (SMTP) listen the TCP connection from its client, the process of initiating the connection on the port (25) is performed by SMTP. Then orderly the connection will be established and the mail is sent instantly. This is the exclusive process followed by SMTP and it has two different models too. Those 2 models are:  

  • End to End method 
  • Store and Forward method 

Let’s see the process done by these two different methods and their uses in detail. 

To perform the communication between two different organizations end to end model is being used and to communicate within the organization, store and forward model is being used. When a client of SMTP tools shop is in need of sending the email will basically contact the host of the destination’s SMTP to send the mail towards the desired destination. The mail will remain safe with the SMTP server till the receiver’s SMTP server copies it. Apart from these two methods, there are two other important terms which constitute the process of SMTP and they are 

  • Client SMTP 
  • Server SMTP 

The client SMTP is the one which generally initiates the process and so it named as client – SMTP and the server SMTP is nothing but the process of responding to the request of the process and thus it is said to be server SMTP. These two systems work one by one automatically when the mail is been sent and received. 

SMTP system basic model 

The user of SMTP model deal with a user agent (UA) such as Netscape, Microsoft outlook, Mozilla and so on. In fact TCP, MTA are used to exchange the mail and when the user is in need to send the email will not basically deal with the MTA because the responsibility to set up the local MTA is carried out by the system admin.  

Basic commands of SMTP 

Here are four basic commands of SMTP are mentioned and they are 

  • HELO 
  • MAIL 
  • RCPT 
  • DATA 

HELO helps in identifying the client to the server where as MAIL initiate the transfer of message. RCPT will follow mail accordingly identifies the addressee also and finally the DATA sends data in a line by line process. 

Finally, altogether the work performed by SMTP is very unique and incomparable. It completes the task of sending and receiving the mail within few seconds and thus it constitutes the important role for the most successful form of communication Email.