Set sender name using SPUtility.SendEmail

SPWeb oWeb = SPContext.Current.Web;

StringDictionary headers = new StringDictionary();

string strFromEmailID = "Name to display <" + fromEmailAddress + ">";

headers.Add("from", strFromEmailID);

headers.Add("to", toEmail);

headers.Add("subject", _subject);

headers.Add("content-type", "text/html");

System.Text.StringBuilder strMessage = new System.Text.StringBuilder();

strMessage.Append(_body);

SPUtility.SendEmail(web, headers, strMessage.ToString());