Sendmail, 3rd Edition

Header Behavior in conf.c

The sendmail program has a built-in understanding of many header names. How those names are used is determined by a set of flags in the source file conf.c supplied with the source distribution. Site policy determines which flags are applied to which headers, but in general, conf.c applies them in the way that is best suited for almost all Internet sites. If you desire to redefine the flags for a particular header name, look for the name’s declaration in the C-language structure definition HdrInfo in conf.c. Be sure to read the comments in that file. Changes to header flags represent a permanent site policy change and should not be undertaken lightly. (We illustrate this process after explaining the flags.)

The flags that determine header use are listed in Table 25-3. Note that each flag name is prefixed with an H_.

Table 25-3. Header flags in conf.c

Flag	§	Version	Description
H_ACHECK	Section 25.6.1	V5 and above	Always process ?flags?
H_BCC	Section 25.6.2	V8.7 and above	Strip value from header
H_BINDLATE	Section 25.6.3	V8.10 and above	Expand macros only at time of delivery
H_CHECK	Section 25.6.4	V5 and above	Process ?flags?
H_CTE	Section 25.6.5	V8.7 and above	Is “content transfer encoding”
H_CTYPE	Section 25.6.6	V8.7 and above	Is “content type”
H_DEFAULT	Section 25.6.7	V5 and above	If already in headers, don’t insert
H_ENCODABLE	Section 25.6.8	V8.8 and above	Field can be RFC2047-encoded
H_EOH	Section 25.6.9	V5 and ...