We have to do the integration with outlook Global address list with Salesforce.
 
We have a requirement where we need to show outlook 365 global contact list in to salesforce Visualforce page.
Global contact list should come from Outlook directly. We will not store the global contacts in to salesforce.
On the run time we should be able to retrieve the global contacts from outlook.
 
GUI Requirement:
Display Contacts in to a dropdownOR
Provide a text box and button. When user enter some string in to text box and click on the button we should get all the global contacts which has entered string in it. If text box is blank and user click on the button than show all the contact for selection. 
Our observation :
I think we need to leverage the REST services provided by office365/outlook to fetch contacts real time. Below link has information related to Outlook API to fetch contacts
https://msdn.microsoft.com/office/office365/APi/contacts-rest-operations#Getcontacts
 
We have tried on the API from the link above. It will give us the contacts for an outlook user from user contact folder but no able to get Global contact list.
Like if I have 15 contact in my outlook contact folder than by using the API I am able to get all 15 contact by not Global contact list.
 
We need some information regarding authentication technique for this integration as well.
 
Please advice.