Completely understand you being desperate for assistance there, but unfortunately the issues you are having there are with your mail services rather than with the software. As a self hosted customer, once the mail leaves our system, it would be for the mail system to deliver those messages. You have seen yourself, the email is getting sent.
The most likely scenario there is that its getting caught in their spam, so it would be well worth getting that checked first of all. There are no access details on file for me to check, but also check to ensure the domain you are sending from has SPF and DKIM records in place. This can cause them to be returned by receiving email services. That again would be a hosting thing though, so if you need more assistance with that you would really need to contact them on this. Sorry we could not be of further assistance there