When a header screening rule set is defined using the H configuration command's * in place of the header's name:

H*:     $>CheckBanned

the header that caused the CheckBanned rule set to be called is not passed in the CheckBanned rule set's workspace. To make design of such rules possible, sendmail offers this ${hdr_name} macro. It contains as its value the current name of the header being processed. The name is stored without a colon. One example of a use for this macro can be seen in Section 25.5.2.

${hdr_name} is transient. If it is defined in the configuration file or in the command line, that definition can be ignored by sendmail. Note that a $& prefix is necessary when you reference this macro in rules (that is, use $&{hdr_name}, not ${hdr_name}).