Unable to set From Email Address using SharePoint Utility send mail

From Email address is not settting correclty using SharePoint Utiliy.I paste code below .Please help

 StringDictionary headers = new StringDictionary();
                        headers.Add("to", "xyz@gmail.com");
                        if (!string.IsNullOrEmpty(SPContext.Current.Site.WebApplication.OutboundMailSenderAddress))
                        {
                            headers.Add("from", SPContext.Current.Site.WebApplication.OutboundMailSenderAddress);
                        }
                        headers.Add("subject", subject);
                        headers.Add("content-type", "text/html");
                        headers.Add("charset", "utf-8");

                        SPSecurity.RunWithElevatedPrivileges(delegate()
                        {
                            SPUtility.SendEmail(SPContext.Current.Web, headers, "Body");
                        });