public async Task <List <DeliveryResult> > DeliverAsync(Message message, List <Recipient> recipients)
        {
            if (message == null)
            {
                throw new ArgumentNullException(nameof(message));
            }
            if (message.Recipients == null)
            {
                throw new ArgumentNullException(nameof(message.Recipients));
            }

            var result = new List <DeliveryResult>();

            foreach (var localRecipient in recipients)
            {
                _log.LogInfo(new LogEvent()
                {
                    EventType = LogEventType.Application,
                    LogLevel  = LogLevel.Info,
                    Message   = $"Delivering message from {message.From} to {localRecipient.Address}",
                    Protocol  = "SMTPD",
                });

                var localAccount = await _accountRepository.GetByIdAsync(localRecipient.AccountId);

                // TODO: Check quotas
                var inbox = await _folderRepository.GetInbox(localAccount.Id);

                var accountLevelMessage = await _messageRepository.CreateAccountLevelMessageAsync(message, localAccount, inbox);

                // TODO: Execute rules

                // TODO: Perform forwarding

                // TODO: Add Trace headers.

                // TODO: Etc

                accountLevelMessage.State = MessageState.Delivered;

                await _messageRepository.InsertAsync(accountLevelMessage);

                // Delete the recipient right away, so that if there is a crash we don't end up sending to this recipient again.
                await _messageRepository.DeleteRecipientAsync(localRecipient);

                result.Add(new DeliveryResult(localRecipient.Address, ReplyCodeSeverity.Positive, "Message delivered."));
            }

            return(result);
        }