Storage usage & costs within Dynamics usually becomes an issue as usage increases and more functionality is deployed (e.g attachments from emails, web portal submissions etc). The folks at Microsoft Labs have created a great tool, Attachment Management, which is described in summation:
"Attachment Management solution is an add-on feature to dynamics 365 CRM Online to manage notes and email attachments using Azure blob storage. Enables business users to optimize use of CRM Online storage and retrieve files on-demand through Dynamics CRM"
I have used this add on before and the latest update works great but there have been previous concerns about it not being supported, as it's developed by Microsoft Labs. I have confirmation that is indeed supported and that the support entails the following:
"If any of the customers are having issues with the solution, those kind of issues will be addressed through support channel. Our team will not help in implementing the solutions at customer’s site."
Great news! You can find the reference support guide here as the one on AppSource at the time of publishing is incorrect!