System.Net.Mail.SendMailAsyncResult.SendToCollectionCompleted C# (CSharp) Method

        private static void SendToCollectionCompleted(IAsyncResult result)
        {
            if (!result.CompletedSynchronously)
            {
                SendMailAsyncResult thisPtr = (SendMailAsyncResult)result.AsyncState;
                try
                {
                    string response;
                    if (!RecipientCommand.EndSend(result, out response))
                    {
                        thisPtr._failedRecipientExceptions.Add(
                            new SmtpFailedRecipientException(thisPtr._connection.Reader.StatusCode,
                                thisPtr._toCollection[thisPtr._toIndex - 1].GetSmtpAddress(thisPtr._allowUnicode),
                                response));

                        if (thisPtr._failedRecipientExceptions.Count == thisPtr._toCollection.Count)
                        {
                            SmtpFailedRecipientException exception = null;
                            if (thisPtr._toCollection.Count == 1)
                            {
                                exception = (SmtpFailedRecipientException)thisPtr._failedRecipientExceptions[0];
                            }
                            else
                            {
                                exception = new SmtpFailedRecipientsException(thisPtr._failedRecipientExceptions, true);
                            }
                            exception.fatal = true;
                            thisPtr.InvokeCallback(exception);
                            return;
                        }
                    }
                    thisPtr.SendToCollection();
                }
                catch (Exception e)
                {
                    thisPtr.InvokeCallback(e);
                }
            }
        }