The Lexmark MX611de has been certified to work with T38Fax.com.

The SIP/T.38 settings are as follows:
  • Fax Transport: T.38
  • STUN Server: Stun Server of your choice
  • Proxy: sip.t38fax.com;transport=udp
  • Registrar: ${SIPProxy}
  • User: YOUR_DID
  • Password: YOUR_PASSWORD
  • Contact: <sip:${SIPUser}@${IPAddr};transport=udp>
  • Outbound Proxy: sip.t38fax.com

lexmark-t38fax