Using Azure Multi-Tenant application without an Office 365 subscription to access users calendar information

Question

We have written a service application that reads Office 365 calendar information from multiple calendars in an organisation (tenant) and does some analysis against the entries. We use the Office 365 REST API for this.
We have multiple client organisations (tenants) that require this functionality so I have followed the steps in @Matthias Leibmann article here: Building Daemon or Service Apps with Office 365 Mail, Calendar, and Contacts APIs (OAuth2 client credential flow)

We used a trial Azure account and a trial Office 365 subscription during development and everything works very well and we have been successfully accessing data for several tenants.
However, when I tried to set up the Multi-Tenant Application using our production Azure account and production Azure Active Directory (AAD) I realised that I can’t define the Application Permissions required for “Office 365 Exchange Online” in the “Permissions to other applications” section of the UI because our production AAD account isn't linked to an Office 365 account.
I assume we could sign up for a developer trial of Office 365 using our production azure account and this would allow us to set the required permissions, but I don’t know what will happen in 30 days when the office 365 trial expires.

Is there a way to define these required permissions without having an Office 365 account linked to our production AAD?
Is this just a tooling issue within the Azure front end or is there a technical reason that we need an Office 365 subscription of our own even though we’re always connecting to some other company’s Office 365 account?

Answer 1

Currently the way it works is you do need an Office 365 subscription, and a Developer Subscription will do. I can check with our Azure folks about what would happen if you added a trial and then let it expire.