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What is ESMTP (Extended Simple Mail Transfer Protocol)?

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  • Difficulty Level : Medium
  • Last Updated : 12 Jul, 2022
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Due to emerging computer science technology and connecting the world through the internet and to have communication between different computers SMTP protocol is being used. Email is widely used by users all over the internet whether to share information in text format or in different multimedia forms. There is a certain set of rules defined for sending and receiving Emails on the internet to provide a safe environment on the internet. When you send an email it does not transfer to the user directly but it goes through a communication process before it reaches its destination and SMTP and ESMTP help in forwarding and feeding the Email. 

SMTP(Simple Mail Transfer Protocol):

First, the user sends mail to its server (eg .gmail) through SMTP, and then through the sender server(Gmail here), it is sent to the receiver’s server mail (can be same or different) through the internet. SMTP help in transferring mail from sender to sender server and then from sender server to receiver servers.

So, SMTP is used to transfer Mail from the sender’s to the receiver’s mail server. For receiving there are different sets of protocols.

SMTP Features:

  • SMTP is a set of protocols for sending mail through the internet. 
  • It is an application Layer protocol.
  • SMTP uses TCP at the transport layer and port numbers 25 and 465. TCP (Transmission Control Protocol) is one of the main protocols of the Internet protocol suite. It lies between the Application and Network Layers which are used in providing reliable delivery services.
  • It is a connection-oriented protocol
  • It is a push protocol. (you can get a new message, new event, etc literally instantly. But you may experience a small time delay in pull protocols.
  • SMTP is the text-based protocol we cannot send audio, videos, images, etc, and cannot send executable binary objects to improve this liability we use SMTP with MIME.

ESMTP(Extended Simple Mail Transfer Protocol):

ESTMP is a set of protocols for sending and receiving electronic messages on the internet. First, Email is sent from sender to sender-server through ESTMP and from sender-server to receiver-server on the internet through ESTMP. ESMTP follows the same protocols as SMTP. It adds more functionality, security, and authentication. In response to some rampant spam on SMTP, an extension for SMTP was released in 1995, which was extended SMTP (ESMTP for short). It has enabled many new functions like it saves bandwidth, protecting servers, and receiving mail there are different protocols such as IMAP.

When you send an email it does not transfer to the user directly but goes through a communication process before it reaches its destination and SMTP and ESMTP help in forwarding and feeding the Email. 

ESMTP features:

  • ESMTP is Extended Simple Mail Transfer Protocol which adds functionality to SMTP(Simple Mail Transfer Protocol).
  • SMTP is responsible for feeding and forwarding e-mails from sender to recipient.
  • SMTP is a set of rules which help in sending Emails over the internet. It is the application layer. Protocol SMTP uses TCP protocol in the transport layer. 
  • ESMTP was introduced in response to rampant spam(huge digital data is sent in bulk) as in SMTP users were not verified before the connection is established. The spammers use fake sender IP addresses so that they cannot be tracked. (Mail spoofing-In tricking users by sending emails in bulk such that users feel they know the entity and generally used to respond)
  • ESTMP adds authentication of the sender. It also adds Transport layer security such as SSL. In ESTMP we can mail send to one or more receivers.
  • We can attach multimedia without MIME.

How is ESTMP different from SMTP?

ESTMP was introduced as an extension to SMTP therefore many new functions were enabled to save bandwidth and protect servers are: 

  • Users were not verified in SMTP as a result of massive-scale scam emails being sent. But in ESMTP authentication of sender is done.
  • On encryption of mail-in SMTP but in ESMTP SSL encryption is done.
  • We cannot attach a Multimedia file in SMTP directly without the help of MMIE but in ESMTP it can be done.
  • We can also reduce size of email in ESMTP but not in SMTP.
  • The main identification feature for ESMTP clients is to open a transmission with the command EHLO (Extended HELLO), rather than HELO.
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