Smtp Anti Spam

• Smtp does not require that the helo be authentic or correct, and spammers invariably use bogus or forged helo names.
• It is taken from the smtp transaction in which the mail was delivered and may be different from the to-address, especially in spam.
• Knowledge of smtp is useful in understanding how spam works.
• Qp encoding also ensures that mail bodies have no lines longer than about 80 characters so as to be fully compliant with smtp (and not to overload older line-oriented mail hosts).
• Most common internet services, including SMTP (e-mail) and HTTP (web services) are defined in IETF RFCs and standards.
• Open Relay: an smtp email server that allows the third-party relay of email messages.
• The relay feature is a part of all smtp-based servers and it has legitimate uses, but spammers have learned how to locate unprotected servers and hijack them to send spam.
• Additional "higher-level" protocols (such as TCP, HTTP, and SMTP) work with IP to define what these packets must look like and how they are to be processed once received.
• Common header-forging (an smtp mail header that has been manipulated by a spammer in order to disguise the message's true origins) tricks include use of phony from- and return-path addresses, bogus helo mail host names, and fictitious routing lines to give a false history to the message.
• A line within an SMTP mail header that begins with the word "Received:" and describes one SMTP handoff between a pair of mail hosts, is the routing line.
• An X-header is an "experimental" SMTP header line, generally used for private purposes by mail hosts.
• Procmail is a popular component of unix-based smtp/pop/imap mail systems, and can be configured for spam filtering.
• MIME is a necessary update to the SMTP-based mail system because SMTP does not allow non-ASCII text data to appear anywhere in e-mail messages.
• The familiar lines showing the to-address and from-address of the message, its subject line, and its date, are technically not part of the smtp header (as properly understood); they are easy to forge and do not contain any trustworthy information that can be used in spam tracing.

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