I just received the new Wireless IP Phone model 8821. when i try to register the phone to Cisco Unity Express, get the next message in the phone: tftp error: wlan rootca.cer.sng tftp error: AppDialRules.xml XMLDefault.cnf.xml(TFTP) File not found: S...

the problem is that the roaming client have a unprotected status and is disable the DNS layer encryption. Do you know if i need to add some rules on the firewall? or How can i solve this problem? I already check that ports 53 and 443 are open in the ...