On the Windows NT User Upgrade Options dialog box, select the "Retain unique NT user name as Notes short name" check box. The Windows NT user name is added as the primary entry in the short name field of the Person document.
The short name is the default for the mail file name and the user ID file name. If you do not select the short name option, Notes generates a short name from the first character of the user's first name, followed by the first seven characters of the last name, for example ssalani, for the user Susan Salani.