sendmail, 4th Edition

Milter smfi_chgheader()

Change and remove headers All sendmail versions

The smfi_chgheader() Milter library routine is used to change the value of existing headers and to remove headers. To conditionally add headers use smfi_addheader() (Milter smfi_addheader() on page 1184). To unconditionally add headers use smfi_insheader() (Milter smfi_insheader() on page 1192).

Before you can modify header values, you first need to declare your intent to do so by including the SMFIF_CHGHDRS flag in the flags portion of the smfiDesc structure:

struct smfiDesc smfilter =
{
    ...
    SMFIF_CHGHDRS,                  /* flags */
    ...

Failure to include this flag causes smfi_chgheader() to return MI_FAILURE every time it is called.

The smfi_chgheader() routine may be called only from within the xxfi_eom() function you write (Milter xxfi_eom() on page 1215). It is called like this:

ret = smfi_chgheader(ctx, name, index, value);

Here, ctx is the common context pointer that was passed to your xxfi_eom() function. The name is the name of the header whose value you wish to change, and value is the new value you wish to assign to that header. On success, MI_SUCCESS will be returned (to ret) or MI_FAILURE will be returned if anything went wrong.

If value is set to NULL, the header will be removed.

The index is a count (not an offset) and must be greater than zero. The index should normally be set to one in order to change the value of the first occurrence of a header with the name. Some header names can appear multiple times, however (the ...