(starting with white-space). Ex-ASCII chars could've been interpretted as
white-space.
parse_header_field() now supports "obsolete" header field syntax
(e.g. "from<white-space>:data").
The sender and sender_address fields (passed to external mail processors)
are now parsed from the received message header (if specified) over-riding
the SMTP "MAIL FROM" command "reverse-path" value.