We have recently Implemented Microsoft graph API in our production environment and 5 email listeners are working with this setup to read inbound emails. Though the email listeners are able to read and parse the inbound emails successfully, we are getting the below exceptions from time to time on a daily basis. And this is happening from very first day of the deployment in production.
@AvisekD5 The Access Token which your application is using while communicating to Microsoft Graph got expired. you need to talk to some one Azure Portal /AD Team. please refer below link to find more on authentication