Since Microsoft have moved outlook/live/hotmail accounts to outlook.office365.com, using EWS service to send the mail..
I have created the WebApp and registered it
https://apps.dev.microsoft.com
Using the end points for the Authorization
https://login.microsoftonline.com/common/oauth2/v2.0/authorize
Using the end point to get access token
https://login.microsoftonline.com/common/oauth2/v2.0/token
Request the below scopes as the part of authorization
scope=openid+offline_access+profile+https:%2f%2foutlook.office.com%2fmail.readwrite+https:%2f%2foutlook.office.com%2fmail.send
Since EWS required the full scope as per the msdn.
Connecting to EWS using access token getting error:
var ewsAuth = new Rebex.Net.Ews();
ewsAuth.Connect("outlook.office365.com");
string pattern2 = string.Format("user={0}{1}auth=Bearer {2}{1}{1}", creds.Email, '\x1', creds.AccessToken);
string token2 = Convert.ToBase64String(Encoding.ASCII.GetBytes(pattern2));
//invalid token error
ewsAuth.Login(creds.AccessToken, EwsAuthentication.OAuth20);
ewsAuth.SendMessage("john@example.org", "Test 1", "Hello world!");