I followed the tutorial below to get mail using outlook api.
This works, but requires the user to login every time to give access. Is there a way to give permanent / offline access? Similar to how gmail api works (access to when your not at your keyboard)
Absolutely! In order to get offline access, you need to add the
offline_access scope to your requested scopes. This will result in a refresh token being sent along with your access token. You can use the refresh token to get a new access token when the current one expires. See the "Refresh the Access Token" section of https://azure.microsoft.com/en-us/documentation/articles/active-directory-v2-protocols/#oauth2-authorization-code-flow.