SpUtil.SendMail using Html body text

var emailFromAddress = _properties["EmailFromAddress"].ToString();
           var emailToAddress = _properties["EmailDistributionGroup"].ToString();
           var webAddress = _properties["WebSiteOfLibrary"].ToString();

           var subject = "New Report - " + DateTime.Now.ToString("dd MMM yyyy");

           StringDictionary messageHeader = new StringDictionary();
           messageHeader.Add("to", emailToAddress);
           messageHeader.Add("from", emailFromAddress);
           messageHeader.Add("subject", subject);
           messageHeader.Add("content-type", "text/html");

           using (SPSite site = new SPSite(webAddress))
           {
               using (SPWeb web = site.OpenWeb())
               {
                   DateTime timeNow = DateTime.Now;
                   var sb = new StringBuilder();
                   sb.Append(
                       "<STYLE TYPE='text/css'>body, html{font-color:#000;font-family:arial;font-size:8.0pt}</STYLE>");
                   sb.AppendFormat("<div style='font-size:11pt;font-family:calibri'>Results between {0} and {1}</div><br/><br/>", LastRun.ToString("dd MMM yyyy hh:mm tt"), timeNow.ToString("dd MMM yyyy h:mm tt"));
                   sb.AppendFormat("<div style='font-size:11pt;font-family:calibri'>Total: {0}<br/><br/>", total);
                   sb.AppendLine(HTMLResults);

                   SPUtility.SendEmail(web, messageHeader, sb.ToString());
               }
           }