Drupal Authentication with ActiveDirectory
I have the following set of parameters that allow authentication by Active Directory 2003:

server type: "Active Directory LDAP"
server address: ad.example.com
ldap port: 389
binding method for Searches: Bind with Users Credentials
base DNs for LDAP user entries: cn=users,dc=example,dc=com
username attribute: sAMAccountName
expression for user DN: %username@company.com
email attribute: mail


I think the problem mainly stems from the fact that AD typically does not have the login name in the LDAP DN.