Simple Mail Transport Protocol. This is the standard protocol used on the Internet to send mail to and between mail servers and clients. This is the protocol Nesox Email Marketer uses to send and route its mail messages.
The SMTP Protocol is based on a standard set forth under RFC 821.
A conversation is established with a SMTP server by connecting to port 25 on the SMTP server. After the initial connection, the client (Email Marketer) sends a HELO command followed by a domain name. This tells the SMTP server to whom it is talking to. The SMTP server may decide to terminate the connection at that point if it does not wish to speak to the specified domain.
If the HELO command is accepted by the remote server, the SMTP client issues a MAIL-FROM command followed by the "from address" of the e-mail being sent. Once again, the SMTP server may decide to terminate the connection if it does not wish to receive mail from the specified sender.
NOTE: Some SMTP servers may do a reverse lookup on the domain name specified for the HELO or FROM command. If the IP address of the SMTP client is not registered to that domain, the client may be considered an imposter, and the connection will be dropped.
After the from address is accepted, the SMTP client issues a RCPT-TO command followed by the address of the intended recipient. At this point the SMTP server has the opportunity to reject mail being sent to the specified address. For example, some SMTP servers will only accept mail for local users.
The SMTP client may issue multiple RCPT-TO commands to the server, thus adding more recipients to the message. When the SMTP client is through adding the recipients to the message, it issues the DATA command to the server.
If the DATA command is accepted, the SMTP client then proceeds to send the message headers, followed by a blank line, followed by the message body and file attachment data. When the SMTP client is through sending the message data, it sends a carriage return, followed by a period, followed by a carriage return, to indicate the end of the message.
At this point the SMTP server acknowledges the receipt of the message data. The SMTP client may then proceed to send another message, or can send the QUIT command to terminate the conversation.
Email Marketer goes a little further that SMTP where supported by using Extended commands such as pipelining and authentication.
Email Marketer complies with the following protocols relating to email.
821 The SMTP protocol
822 Standard for the format of ARPA Internet text messages
974 Mail routing and the domain system
1854 SMTP Service Extension for Command Pipelining
1869 SMTP Service Extensions (ESMTP) (Obsoletes RFC1651)
1891 SMTP Service Extension for Delivery Status Notifications
1939 Post Office Protocol - Version 3. (Obsoletes RFC1725)
2045 Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. (Obsoletes RFC1521 RFC1522 RFC1590)
2046 Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types. (Obsoletes RFC1521 RFC1522 RFC1590)
2047 MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text. (Obsoletes RFC1521 RFC1522 RFC1590)
2554 SMTP Service Extension for Authentication