FTP Connection Fails

I am trying to connect to a FTP server using UserName, Password and Domain. But this Fails with the error "{"530 Login incorrect." & vbCrLf} System.Exception". Below is my code:

Dim ConnectionURLString As String = "ftp://ftp.xxxxxx.com"
    Dim RemotePathString As String = "ftp://ftp.xxxxxx.com"
    Dim UserNameString As String = "username"
    Dim PasswordString As String = "password"

    Dim request As FtpWebRequest = DirectCast(WebRequest.Create(RemotePathString), FtpWebRequest)
    request.Method = WebRequestMethods.Ftp.ListDirectoryDetails
    request.Credentials = New NetworkCredential(UserNameString, PasswordString, ConnectionURLString)
    request.UsePassive = True
    request.UseBinary = True
    request.EnableSsl = False
    Dim response As FtpWebResponse = DirectCast(request.GetResponse(), FtpWebResponse)

When I structure the Request.Credentials without the Domain (ConnectionURLString), the connection does not fail. How do I use the domain correctly to connect to the FTP server?