var sourceList = project.Lists["SourceList"];
var response = project.Variables["Response"].Value;
var regex = new Regex(@"([a-z0-9_-]+\.)*[a-z0-9_-]+@[a-z0-9_-]+(\.[a-z0-9_-]+)*\.[a-z]{2,6}");
regex.Matches(response).Cast<Match>().ToList().ForEach(m=>sourceList.Add(m.Value.Trim()));