What is SMTP

SMTP stands for Simple Mail Transfer Protocol, it is a protocol used to send e-mail on the Internet. SMTP is a set of rules regarding the interaction between a program sending e-mail and a program receiving e-mail. For detail information about SMTP, please refer to RFC 821 Simple Mail Transfer Protocol.

SMTP is Internet’s standard host-to-host mail transport protocol and traditionally operates over TCP on port 25. So for Windows 2000 or up user, you can do the following to send out an email message without any email clients such as Ms Outlook

• Click “start” --> “Run“, type “CMD”
• Type “telnet“ then “enter”. Now you will be in the environment of Microsoft telnet client in which you can use commands to send out email message.
• Type “open 127.0.0.1 25”, 25 means port 25. Now you are connected with your local SMTP server if you enable SMTP in your IIS.

Below SMTP example shows mail sent by Smith at host test.com to Jones and Brown at host beta.nl.
S: means you, R: means response from server.

S: HELO yourdomain
R: 250 OK

S: MAIL FROM:<smith@test.com>
R: 250 OK

S: RCPT TO:<Jones@beta.nl>
R: 250 OK

S: RCPT TO:<Brown@beta.nl>
R: 250 OK

S: DATA
R: 354 Start mail input; end with <CRLF>.<CRLF>
S: Blah blah blah...
S: ...etc. etc. etc.
S: <CRLF>.<CRLF>
R: 250 OK

Why you need a SMTP server

SMTP server is a mail server that supports the SMTP protocol for email transfer. SMTP server is the server that distributes email messages on Internet. Before your email message reaches its destination, it normally will pass several SMTP servers on internet. Those SMTP servers have the responsibility to make sure that your email message will be delivered to the right destination.

Our application will prepare your email message in the format that complies with RFC 2822 Internet Message Format and send it the SMTP server you specify in SETTING\global.

You need to specify a SMTP server which our application can communicate to for mail distribution.