How do I configure Inbound Email for Exchange Online

[Dan Rico]

I need to be able to connect an Exchange Online mailbox to our Jira Cloud for incoming emails but do not want to use a User Principal. 

In the past it was possible to set up an Azure App Registration, give it POP3 and openid permissions and then use a client secret to allow Jira to read emails using that Service Principal. I cannot find any settings that would allow this. 

The only option I have found is to use a Shared Mailbox and my own User Principal to set this up but not a Service Principal/App Registration.