Sendmail 8.13.3 Programmer's Guide

Milter APIs
Callbacks
Chapter 240
SMFIS_DISCARD Accepts and discards the message. The filter
application does not call the xxfi_abort()
callback to abort the message.
SMFIS_ACCEPT Accepts the recipient. The filter application does
not call the xxfi_abort() callback to abort the
message.
The xxfi_header() Callback
The xxfi_header() handles the message header and returns the
SMFIS_CONTINUE value to the calling filter application. You can call
xxfi_header() multiple times after calling the xxfi_envrcpt()
callback and before calling the xxfi_eoh() callback, and once for each
message header. Later filter applications can observe the header changes
or additions made by earlier filter applications.
The declaration of xxfi_header() is as follows:
#include <libmilter/mfapi.h>
sfsistat (*xxfi_header)(
SMFICTX * ctx,
char * headerf,
char * headerv
);
Arguments
You must call xxfi_header() with the following arguments:
ctx Specifies an opaque context structure.
headerf Specifies the header field name.
headerv Specifies the header field value. The header content
can include folded white space, that is, multiple lines
followed by a white space. The filter application
removes the trailing line terminator (CR or LF).
The xxfi_eoh() Callback
The xxfi_eoh() callback handles the end of message headers and
returns SMFIS_CONTINUE to the calling filter application. You must call
xxfi_eoh() only once after all the headers are sent and processed.
Argument