Build a java application for Microsoft Exchange email using Oauth2 authentication

We need a java application that reads and send emails, both text and attachments, through microsoft outlook.

The use case is as follows:

It's a multitenant application in which the user will sign in with his azure registered account in a cloud platform, and get the authentication code, and will input it into his on premise server.

This part we already have.

What we need is the code to actually handle the authentication and emails.

There is no preference for how the emails will be handled (whether it is IMAP, rest or graph).