Microsoft Graph API to receive mails

I want to integrate Outlook email services into my CRM to receive and send emails. I found that MIcrisift provides graph API's in order to achieve this.

The link of the module is : https://github.com/microsoftgraph/nodejs-webhooks-rest-sample 

 

I have done the configuration successfully as per the instructions given in above link. After doing it I found it throws some error which I posted on github in the link : https://github.com/microsoftgraph/nodejs-webhooks-rest-sample/issues/21

 

I still did not find any workable solution for this error. 

 

Any response will be appreciated.