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Sendmail, 3rd Edition by Bryan Costales

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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 ...

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