MailSite-User account Where is the MailSite-User account created by the installer? The MailSite-User NT account is created by the installer. This only applies to Windows 2000 server. There is no option to create a new NT user account through the installer for NT 4.0 Server, due to limitations in the operating system itself. In MailSite 6 and later, the installer will create a NT account called 'MSIISUSER' for use with MailSite and MailSite Express