how to make postfix alter the "From" header on outbound messages to mat IP

[list]

So here's the problem: 

  An unusual server rejects mail on the basis that the domain portion
  of the FROM address in the header does not match the IP address of
  the server.

So I need to compose a message like this:

  From: anything@<let postfix choose>
  To: ...
  Subject: ...

and I need postfix to replace the <let postfix choose> with whatever
my external IP address is at the moment.

Can postfix handle this?