smfi_insheader(3N)

NAME

smfi_insheader() — prepends a header to the current sendmail message

#include <libmilter/mfapi.h>  

int smfi_insheader(  
    SMFICTX *ctx,
    int hdridx,
    char *headerf,
    char *headerv
); 

ctx: Specifies the opaque context structure.
hdridx: Specifies the location in the internal header list where the header must be inserted. A value of 0 (zero) places the header in the beginning of the header.
headerf: Specifies the header name, which is a non-NULL, null-terminated string.
headerv: Specifies the header value to be added. A header value is a non-NULL, null-terminated string and can be an empty string.

smfi_insheader() prepends a header to the current message. smfi_insheader() can be called only from the xxfi_eom() function.

smfi_insheader() does not change existing headers of a message. To change the current value of a header, use the smfi_chgheader() routine.
A filter that calls smfi_insheader() must set the SMFIF_ADDHDRS flag in the smfiDesc_str structure passed to the smfi_register() routine.
For the smfi_insheader() filter, the order in which filters are placed is imporant. Filters placed later in the sequence will observe the changes already done by the earlier filters.
If the value of hdridx larger than the number of headers in the message, the header is simply be appended.
The name and the value of the header are not checked for standards compliance. However, each line of the header must be under 2048 characters. If longer headers are needed, multi-line header must be used. To make a multi-line header, insert a linefeed (ASCII 0x0a, or \n in C) followed by at least one whitespace character, such as, a space (ASCII 0x20) or tab (ASCII 0x09, or \t in C). The linefeed must not be preceded by a carriage return (ASCII 0x0d); the MTA adds this automatically. It is the responsibility of the filter writer to ensure that standards are not violated.

smfi_insheader() returns MI_FAILURE due to the following reasons:

smfi_insheader() returns MI_SUCCESS on success.

int ret; 
SMFICTX *ctx; 

... 

ret = smfi_insheader(ctx, 0, "First", "See me?"); 

smfi_insheader() was developed by the Sendmail Inc.