SMTP - Simple Mail Transfer Protocol
Posted by Harisinh | Posted in | Posted on 10:33 PM
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The Simple Mail Transfer Protocol (SMTP) provides a basic e-mail facility. SMTP is the protocol that transfers e-mail from one server to another. It provides a mechanism for transferring messages among separate servers. Features of SMTP include mailing lists, return receipts and forwarding. SMTP accepts the incoming message and makes use of TCP to send it to an SMTP module on another servers. The target SMTP module will make use of a local electronic mail package to store the incoming message in a user’s mailbox. Once the SMTP server identifies the IP address for the recipient’s e-mail server, it sends the message through standard TCP/IP routing procedures.
Since SMTP is limited in its ability to queue messages at the receiving end, it’s usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving messages that have been received for them at their local server. Most mail programs (such as Eudora) let you specify both an SMTP server and a POP server. On UNIX-based systems, sendmail is the most widely-used SMTP server for e-mail. Earlier versions of sendmail presented many security risk problems. Through the years, however, sendmail has become much more secure, and can now be used with confidence.
A commercial package, sendmail, includes a POP3 server and there is also a version for Windows NT. Hackers often use different forms of attack with SMTP. A hacker might create a fake e-mail message and send it directly to an SMTP server. Other security risks associated with SMTP servers are denial-of-service attacks. Hackers will often flood an SMTP server with so many e-mails that the server cannot handle legitimate e-mail traffic. This type of flood effectively makes the SMTP server useless, thereby denying service to legitimate e-mail users. Another well-known risk of SMTP is the sending and receiving of viruses and Trojan horses. The information in the header of an e-mail message is easily forged. The body of an e-mail message contains standard text or a real message.
Newer e-mail programs can send messages in HTML format. No viruses and Trojans can be contained within the header and body of an e-mail message, but they may be sent as attachments. The best defence against malicious attachments is to purchase an SMTP server that scans all messages for viruses, or to use a proxy server that scans all incoming and outgoing messages. SMTP is usually implemented to operate over TCP port 25. The details of SMTP are in RFC 2821 of the Internet Engineering Task Force (IETF). An alternative to SMTP that is widely used in Europe is X.400.
This is what all about the SMTP. How it sends the message from sender to receiver and how it guides the message to reach at the receiver.
Enjoy.....
The Simple Mail Transfer Protocol (SMTP) provides a basic e-mail facility. SMTP is the protocol that transfers e-mail from one server to another. It provides a mechanism for transferring messages among separate servers. Features of SMTP include mailing lists, return receipts and forwarding. SMTP accepts the incoming message and makes use of TCP to send it to an SMTP module on another servers. The target SMTP module will make use of a local electronic mail package to store the incoming message in a user’s mailbox. Once the SMTP server identifies the IP address for the recipient’s e-mail server, it sends the message through standard TCP/IP routing procedures.
Since SMTP is limited in its ability to queue messages at the receiving end, it’s usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending e-mail and either POP3 or IMAP for receiving messages that have been received for them at their local server. Most mail programs (such as Eudora) let you specify both an SMTP server and a POP server. On UNIX-based systems, sendmail is the most widely-used SMTP server for e-mail. Earlier versions of sendmail presented many security risk problems. Through the years, however, sendmail has become much more secure, and can now be used with confidence.
A commercial package, sendmail, includes a POP3 server and there is also a version for Windows NT. Hackers often use different forms of attack with SMTP. A hacker might create a fake e-mail message and send it directly to an SMTP server. Other security risks associated with SMTP servers are denial-of-service attacks. Hackers will often flood an SMTP server with so many e-mails that the server cannot handle legitimate e-mail traffic. This type of flood effectively makes the SMTP server useless, thereby denying service to legitimate e-mail users. Another well-known risk of SMTP is the sending and receiving of viruses and Trojan horses. The information in the header of an e-mail message is easily forged. The body of an e-mail message contains standard text or a real message.
Newer e-mail programs can send messages in HTML format. No viruses and Trojans can be contained within the header and body of an e-mail message, but they may be sent as attachments. The best defence against malicious attachments is to purchase an SMTP server that scans all messages for viruses, or to use a proxy server that scans all incoming and outgoing messages. SMTP is usually implemented to operate over TCP port 25. The details of SMTP are in RFC 2821 of the Internet Engineering Task Force (IETF). An alternative to SMTP that is widely used in Europe is X.400.
This is what all about the SMTP. How it sends the message from sender to receiver and how it guides the message to reach at the receiver.
Enjoy.....
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