Simple Mail Transfer Protocol Simulator

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Protocol Description

SMTP (Simple Mail Transfer Protocol) is used to transfer email messages. SMTP operates over TCP (Transmission Control Protocol) in client-server mode for reliable transfer of data. The protocol simulation deals with the main commands (sent in approximately the order below):

The simulation supports a limited range of response codes:

After the client connects to the server using TCP, the server reports its readiness with a 220 Server ready response. The client names itself in HELO, to which the server normally gives a 250 Server hello to client response. To send mail, the client issues MAIL FROM and normally gets a 250 Sender OK response. Recipients are named in RCPT TO, normally obtaining 250 Recipient OK responses. However the server can reject a sender or recipient with a 550 Sender invalid or 550 Recipient invalid response. Once all parties have been named, the client sends DATA to begin message transmission; a 354 Send mail response is expected from the server. At this point, the real protocol would send the lines of the message followed by a full stop. In the simulation, a single Mail Message command stands for this. The server will normally give a 250 Message accepted response and further messages can be sent. Finally, the client sends QUIT and the server responds with a 221 Server closing code. At this point the TCP connection is broken.

Protocol Parameters

This simulation has no parameters.

Protocol Simulation


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Last Update: 11th February 2011
URL: http://www.cs.stir.ac.uk/~kjt/software/comms/jasper/SMTP.html