Where is the Log for Azure Service Bus Topic Subscriptions Messages Sent/Delivered?

I have an accute problem that I can't see what is going on in the ServiceBus. I need to find/activate the logs. Thanks for any quick tips!

My unanswered, identical, question on Stack:

(See where-is-the-log-for-azure-service-bus-topic-subscriptions-messages-sent-deliver there since I was not trusted to post a link here although I pay for MSDN :-))

After searching in vain... where can I see a log/list of which Azure Service Bus Messages (content?) have been sent to a given Topic+Subscription and which ones have been delivered? Do I have to activate a special feature? If so, which? New or "classic" Azure Management Portal?

Thanks!