Details: Protocol TBR
Protocol TBR is not a standalone protocol; rather it is an extension of the SMTP protocol. TBR stands for “Transferred By Reference.” When this extension is used, the Simple Mail Transfer Protocol (SMTP) then uses HTTP and XAM (Extensible Access Method) infrastructures to transfer the message. Protocol TBR or the TBR extension of SMTP specifies three mandatory arguments and one optional argument. The mandatory ones are forwarding count, an eXAM URI, and an end-mark tag.
The optional argument involves trace headers. According to the September 2007 draft by Douglas Otis of Trend Micro and John Leslie of JLC.net proposing protocol TBR to the IETF, the TBR extension of SMTP helps reduce the spread of unwanted email messages as well as reduces the harvesting of email addresses by spammers. By eliminating acknowledgments such as “unknown recipient” that are sent back to senders, email harvesters have one less tool for validating an email address.
Protocol TBR establishes a means of checking senders and recipients. For example, if a sender has been deemed abusive or a spammer or if the recipient is invalid, the message may not be fetched and delivered, thus reducing the number of undesirable email messages. It also reduces the heavy network loads imposed upon servers due to SPAM.
Associated Protocol TBR Applications:
Email applications such as Microsoft Outlook and Exchange