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FTP vs SMTP | difference between FTP and SMTP

This page on FTP vs SMTP describes difference between FTP and SMTP. Also refer FTP vs HTTP which mentions difference between FTP and HTTP.


FTP stands for File Transfer Protocol. It is used to send/receive file from the remote computer. It is defined in RFC959. FTP establishes two connections between client system and server system, one for control information and the other for data to be transfered. Control information carry commands/response. Authentication need to be done initially by way of validating username and password. Once it is done files can be transferred between two systems. FTP handles both binary and text format files.

SMTP stands for Simple Mail Transfer Protocol. SMTP provides a protocol for two computers to exchange electronic mail usign a TCP connection. In other words, it is the protocol used by e-mail servers to forward messages across the TCPIP network. The client computer which usually initiates the e-mail message uses the SMTP to send the e-mail to the local server delivery. It is defined in RFC821,RFC822 and RFC974.

As mentioned SMTP communicates with the network via TCPIP protocol stack. SMTP communication occurs through TCP port 25 on SMTP server.

The communication between client and server in the SMTP process consists of about 4 character commands from client to the server and 3 digit response codes from the server to the client as mentioned below in the table. SMTP server response codes are very important in case there is some problem to debug it further from networking point of view.

As we know now that main difference between FTP and SMTP is that with FTP user can send and receive file to and from the computer, While SMTP is used to deliver the mail to the user's mail box configured in the e-mail server.

SMTP Response codes

SMTP response Code Description
221 Domain service closing the transmission channel
250 Requested action completed successfully
450 Action was not taken because mailbox is busy
500 Syntax error: command not recognized
501 Syntax error: problem with parameters or arguments
550 Action was not taken because mailbox was not found
551 User is not local, try sending the message to PATH

Other useful difference between FTP and SMTP protocols are mentioned in the following table:

Feature FTP SMTP
TCP port number 20 and 21 25
RFC reference documents RFC959 RFC821, RFC822 and RFC974
Protocol function Used to transfer files from remote computer after connection is established Used to e-mail send messages between computers. This is done either using SMTP server or using mail function.

Following links help one understand difference between HTTP and SMTP also.


Basics of OSI and TCPIP layers
Networking tutorial

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