Class Macros

A class macro is one whose symbol can represent multiple words. Those words can be declared in the configuration line or read from an external file or from the output of an executed program.

CXword word ... FX /file FX |program

The symbolic name (here X) is either a single letter or a multi-character name. If multi-character, it must be surrounded by curly braces:

C{XXX}word word ... F{XXX} /file  F{XXX} |program

The sendmail program reserves all but class names that begin with an uppercase letter for its own internal use. Class macros are usable only in the LHS of rules. A $= prefix matches a token to any word in the class. A $~ prefix matches if the token is not in the class.

• $=e
• Determines whether or not a Content-Transfer-Encoding: type will be quoted-printable encoded. The default contents for this class are bit, bit, and binary (see §32.5.1).
• $=k
• Lists the UUCP names of the local host (see §32.5.2).
• $=m
• Lists all the known domain names for the local host. Available to rule sets but not currently used by the m4 technique (see §32.5.3).
• $=n
• Determines the Content-Type: headers that are prevented from being converted from 8- to 7-bits. The default content for this class is %multipart/signed (see §32.5.4).
• $=q
• Determines the Content-Type: headers that should not be converted from from 8- to 7-bits with base64 encoding. By default this class is empty (see §32.5.5).
• $=s
• Lists Content-Type: header message subtypes that should be treated the same as rfc822. By default this list contains only rfc822 (see §32.5.6).
• $=t
• Lists "trusted" users who may specify an alternative sender with the -f command-line switch (see §32.5.7).
• $=w
• Lists all the hostnames by which the local host can be known. Either found by sendmail at startup, or declared in the configuration file, or listed in the sendmail.cw file (see §32.5.8).