Well, I've just had a response off Nigel, which was "the issue still lays with Microsoft to resolve and at this time they(Microsoft) will need to resolve from their end.". So, not exactly a wealth of information there!
You need to clarify and fully explain in detail what you mean by configuring the server to accept Quickbooks online mail server host names and ip addresses.
Are you meaning solution 3 is the below link your helpdesk has provided?
https://quickbooks.intuit.com/learn-support/en-uk/manage-customers/3-solutions-for-when-customers-ar...
