You've not included the entire header (missing a trailing ')')
I copied it verbatim.
, and
it's not rewritten, actually.
spamass-milter cooks up a Received: header for sending to SA so that
SA rules can trigger on the contents of it, but it's not complete,
because at the time spamass-milter processses the mail, nothing has
yet been accepted by the MTA.
It probably could include the time and the semi-colon by modifying how
the header is cooked up, but right now it doesn't.
It would be good to at least be RFC2821 compliant, don't you think?
--
Daniel