spnego sso failure redirect

[cbl016]

I have spnego single sign on set up on zimbra and it works fine when a domain user accesses zimbra but when a client that is not on the domain tries to access zimbra it takes them to a web page that says "UNAUTHORIZED" instead of redirecting them to the zimbraSpnegoAuthErrorURL (/zimbra/?ignoreLoginURL=1).

If a non-domain user goes straight to the zimbraSpnegoAuthErrorURL (/zimbra/?ignoreLoginURL=1) then it will allow them to login normally which is what I would like when spnego authentication fails.

Any help getting this figured out would be appreciated.