Can Postfix add/change/remove mail header fields?

Hello,

it seems to be well-known for years, but I noticed it just today:
Spamassassin records spam points for the header "X-Library: Indy"
because some spam-sending tools are apparently using the Indy
TCP/IP library - as I do, but of course not for spam sending
(but for mailing invoices to customers).

Since omitting the "X-Library" header field would require me
to recompile the complete Indy library (with Delphi), I thought
about header rewriting within my Postfix mail server (where all
my mails pass through anyway).

Something like "remove 'X-Library'" would be sufficient; more
sophisticated would be "if 'From'=='accounting@...' then...".

Is it possible?

Thank you,

Matt

PS: Another bunch of spam points are recorded because of
"rfkindy" appearing within the MIME boundary. I guess
"changing the MIME boundary" during transport is something
which _no_ MTA can achieve, huh?!