3.1.5.3.3 Receiving the NTLM_REJECT REPLY Command
Expected AUTH_STATE: authenticate_data_sent
A REPLY command with NTLM_CommandCode set to NTLM_REJECT indicates that the server has failed to authenticate the client by using NTLM. This command marks the end of the Telnet: NTLM Authentication Protocol.
If the client's AUTH_STATE is equal to authenticate_data_sent, the client MUST set AUTH_STATE to authentication_complete, and MUST proceed with negotiation for other options, as specified in [RFC855].<7>
If the AUTH_STATE is not equal to authenticate_data_sent, the client SHOULD treat this as an error condition, and then take an appropriate action most suitable for the implementation.<8>