This thread began in May.  It is now the end of September.  This matter is not resolved as you say it is.  I don't know what is more absurd, your initial response being marked as resolved or your later reply to a customer comment where you actually double down and defend marking an unresolved matter as resolved.

News Flash: Telling someone to open a support ticket is not a resolution, especially when other users continue to report the same problem for months on end.  QB Enterprise costs far too too justify the many hours of troubleshooting it takes to remain functional. 

In wake of yet ANOTHER QuickBooks support failure I was able to find ANOTHER work around. If you are familiar with QB, I am sure you already come up with a handful of workarounds for other issues.

Disable Cached exchange mode by unchecking the box located under Account Settings > Account Settings > Change.

Hopefully your QuickBooks problem isn't replaced by an Outlook problem. Good luck!