Dailymail messages are sent the same way as manually sent messages, so if manually sent messages are received as expected followups should be received too. Could there be a delay at the server and you have now received the messages? Could the messages have found their way to your Spam folder and been missed? Could you have exceeded a limit for sending imposed by your web host, which might be seen in their terms of service?
If SMTP is enabled on the Configuration page, and by enabling the SMTP log feature (Check "Always write SMTP logfile" in the Mail Sending Method section) we can confirm that followup messages are indeed sent to the server as expected. The log is written to the ListMail /attach folder. Once the messages are sent to the server, it's up to the server to deliver and client to receive them.
Regards