i found a solution, which is working (http://www.t38faxvoip.com and http://www.sipcall.at for t.38). but not for sending PDF. when i use windows fax and scan there ist no problem. when i use Outlook 2003, exchange 2007 and faxmailtransport, then outlook sends a message, that the attachment is not correct and cannot be sent.
???
thanks for your ideas.