public async Task EventTest() { /* Arrange */ var client = new SmtpClient("email-smtp.us-east-1.amazonaws.com", 587) { Credentials = new NetworkCredential("AKIAIU3L5KJH6W777CRA", "Akjr30PTOD1Q2NyqjjkeDuUaxk4ralbrPp2VbT4FnD4u"), EnableSsl = true }; client.ProgressChanged += ClientOnProgressChanged; var froms = new List <string>(); /* Act */ for (var i = 0; i < Count; i++) { froms.Add("*****@*****.**"); } await client.SendBulkMailAsync("*****@*****.**", froms, "Test", "Test"); }