Remove a recipient from the current message's envelope.
||Called only from xxfi_eom.
||smfi_delrcpt removes the named recipient from the current message's envelope.
||Opaque context structure.
||The recipient address to be removed, a non-NULL, null-terminated string.
||smfi_delrcpt will fail and return MI_FAILURE if:
Otherwise, it will return MI_SUCCESS
- rcpt is NULL.
- Deleting recipients in the current connection state is invalid.
- A network error occurs.
- SMFIF_DELRCPT was not set when smfi_register was called.
The addresses to be removed must match exactly. For example, an address and its expanded form do not match.