A client is attempting to log in to a web application that requires authentication. The following HTTP headers are sent by the client:

GET /owa/ HTTP/1.1

Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

User-Agent: curl/7.26.0

Host: 10.0.0.14

Accept: */*

Accept-EncodinG. gzip,deflate

The web server is responding with the following HTTP headers:

HTTP/1.1 401 Unauthorized

Content-TypE. text/html

Server: Microsoft-IIS/7.5

WWW-AuthenticatE. NTLM

DatE. Wed, 16 Aug 1977 19:12:31 GMT

Content-LengtH. 1293

The client has checked the login credentials and believes the correct details are being entered.

What is the reason the destination web server is sending an HTTP 401 response?