C# ASP.net attach file to email

II have an asp.net form with a FileUpload function. This section is working correctly:

protected void UploadCertificate(object sender, EventArgs e)
    {
        if (quality_certificate.HasFile)
        {
            string fileName = quality_certificate.FileName;
            quality_certificate.SaveAs(MapPath("fileuploads/" + fileName));
            LabelQC.Text = "File " + fileName + " has uploaded";
        }
        else
        {
            LabelQC.Text = "No file uploaded";
        }
    }

However when I try to retreive this file on submitting the form, it will not attach to the email presumably because the MapPath line is incorrect? Any advice welcome!

Attachment attachFile = new Attachment(Server.MapPath("fileuploads/" + quality_certificate.FileName));

For example when its hard coded it works:

Attachment attachFile = new Attachment(Server.MapPath("fileuploads/logo.gif"));// THIS WORKS


The directory is fileuploads within the root of the web site.
Permissions set to 775.
identity impersonate="true"