Here's list of Fax Connector Options for Exchange Server

• Fax Exchange
  Fax Exchange Product info
  Fax Exchange Features
  

• GFI Fax Maker
  

• PP-COM Telecommunication + Networking GmbH
  

• Top Call
  

• Network Faxing with Microsoft Exchange and Outlook
  SDSI & Fax Sr.
  

• This one is not that clear that it works with Exchange server, yet
  Biscom
  FAXCOM® for Exchange software runs as an NT service that integrates with Microsoft Exchange
  

• NT Fax
  

• Gold-fax
  

• FAXserve for Windows NT by Computer Associets
  

• Faxination 3.0