Simple Mail Transfer Protocol
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This document discusses SMTP (Simple Mail Transfer Protocol). It defines SMTP as an application layer protocol used to transfer email between servers. It describes the basic model of SMTP including the roles of user agents (UA), mail transfer agents (MTA), and how emails are transferred between MTAs across the network. It also lists some common SMTP commands used in the transfer process such as HELO, MAIL, RCPT, and DATA.
Simple Mail Transfer Protocol
- 1. SMTP Presented by: Rabin BK 1
- 3. INTRODUCTION âş An application layer protocol âş SMTP server is always on listening mode âş As soon as it listens for a TCP connection from any client, the SMTP process initiates a connection on that port (25) âş The client process sends the mail instantly after successfully establishing connection 3
- 4. TERMINOLOGIES âş User Agent(UA): Prepares the message and send it to the MTA âş Mail Transfer Agent(MTA): Transfers the mail across the network to the receivers MTA âş Note: To send mail, a system must have the client MTA, and to receive mail, a system must have a server MTA 4
- 5. MODEL OF SMTP SYSTEM âş User deals with the user agent (UA) for example Microsoft Outlook, Netscape, Mozilla, etc âş To exchange the mail using TCP, MTA is used âş The users sending the mail do not have to deal with the MTA it is the responsibility of the system admin to set up the local MTA âş MTA maintains a small queue of mails so that it can schedule repeat delivery of mail in case the receiver is not available âş MTA delivers the mail to the mailboxes and the information can later be downloaded by the user agents 5
- 6. MODEL OF SMTP SYSTEM 6
- 7. SMTP COMMANDS âş HELO â Identifies the client to the server, fully qualified domain name, only sent once per session âş MAIL â Initiate a message transfer, fully qualified domain of originator âş RCPT â Follows MAIL, identifies an addressee, typically the fully qualified name of the addressee and for multiple addressees use one RCPT for each addressee âş DATA â send data line by line 7