keep mail out of bulk folder

Hi, I just setup cyrus+postifx on rh9, and all my mail that I send using smtp (with auth) keeps on going into yahoo's bulk mail folder.  If I send mail from the same machine using Squirrel-Mail, my messages stay in the inbox as usual.  I'm pretty sure my problem is with headers.  When I send mail from sm, it has a header that says:

Received: from x.x.x.x (SquirrelMail authenticated user ben) by mail.example.com with HTTP; Wed, 24 Mar 2004 14:52:04 -0800 (PST)

If I send from outlook (smtp) I have headers that don't look as good.

Received: from x.x.x.x (EHLO example.com) (x.x.x.x) by mta271.mail.scd.yahoo.com with SMTP; Fri, 26 Mar 2004 14:32:30 -0800

Received: from compaqdesktop (unknown [192.168.1.105]) by example.com (Postfix) with ESMTP id 5D81EBD6B for <x@yahoo.com>; Fri, 26 Mar 2004 18:23:16 -0800 (PST)


How can I make postfix give "good" headers when my users use sasl to authenticate so that yahoo won't think it's spam?  Thanks.
-ben