Prepend a header to the current message.
||Called only from xxfi_eom.
||Prepends a header to the current message.
||Opaque context structure.
||The location in the internal header list where this header should
be inserted; 0 makes it the topmost header, etc.
||The header name, a non-NULL, null-terminated string.
||The header value to be added, a non-NULL, null-terminated string. This may be the empty string.
||smfi_insheader returns MI_FAILURE if:
Otherwise, it returns MI_SUCCESS.
- headerf or headerv is NULL.
- Adding headers in the current connection state is invalid.
- Memory allocation fails.
- A network error occurs.
- SMFIF_ADDHDRS was not set when smfi_register was called.
- smfi_insheader does not change a message's existing headers.
To change a header's current value, use
- A filter which calls smfi_insheader must have set the SMFIF_ADDHDRS
flag in the smfiDesc_str passed to
- For smfi_insheader, filter order is important.
Later filters will see the header changes made by earlier ones.
- A filter will receive only headers that have been sent
by the SMTP client and those header modifications by earlier filters.
It will not receive the headers that are inserted by sendmail
This makes the header insertion position highly dependent on
the headers that exist in the incoming message
and those that are configured to be added by sendmail.
For example, sendmail will always add a
Received: header to the beginning of the headers.
hdridx to 0 will actually insert the header
However, later filters can be easily confused as they receive
the added header, but not the
thus making it hard to insert a header at a fixed position.
- If hdridx is a number larger than the number of headers in the message,
the header will simply be appended.
- Neither the name nor the value of the header is checked for
However, each line of the header must be under 2048 characters
and should be under 998 characters.
If longer headers are needed, make them multi-line.
To make a multi-line header,
insert a line feed (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 line feed should NOT be preceded by a carriage return (ASCII 0x0d);
the MTA will add this automatically.
It is the filter writer's responsibility to ensure that no standards
ret = smfi_insheader(ctx, 0, "First", "See me?");