Get inboxinfo from shared/delegated mailbox in Gsuite - google-apps-script

Question

We're using Gsuite Enterprise/Piazzaweb at work. I'm using basic scripts to get information from my own mailbox, no problems there. But I want to pull information from a couple of shared mailboxes in which I'm delegated. For example billing#mycompany.com. But I can't find any information regarding this and if it's even possible to reach a delegated mailbox with App script.
I've been sending e-mails from the delegated mailbox with app script without any problem.
Hopefully somebody can tell me more about this.
Thanks in advance.

Answer 1

In order to use Service Accounts in Apps Script, you have to do the following:
Build the OAuth service for your Service Account with the following library: OAuth2 for Apps Script.
Call the corresponding API by making the corresponding HTTP request via UrlFetchApp.fetch(url, params).
1. Build the OAuth service:
Once you have added the specified library to your script, you have to do this in order to build the OAuth service with delegated credentials, :
const PRIVATE_KEY = '-----BEGIN PRIVATE KEY-----\nxxxxxxxxxxxxxxxxxxxxx\n-----END PRIVATE KEY-----\n';
const CLIENT_EMAIL = 'xxxxxxxxxxxxxxxxxxxxx.iam.gserviceaccount.com'; // Service account email
const USER_EMAIL = 'email_address_to_impersonate'; // Account to impersonate
const SCOPE = 'https://www.googleapis.com/auth/gmail.readonly' // Change according to your preferences
function getGmailService() {
return OAuth2.createService('Gmail: ' + USER_EMAIL)
.setTokenUrl('https://oauth2.googleapis.com/token')
.setPrivateKey(PRIVATE_KEY)
.setIssuer(CLIENT_EMAIL)
.setSubject(USER_EMAIL)
.setPropertyStore(PropertiesService.getScriptProperties())
.setScope(SCOPE);
}
Where PRIVATE_KEY refers to the key found in the Service Account JSON credentials, CLIENT_EMAIL is the Service Account email, and USER_EMAIL refers to the email address whose INBOX you want to access.
It's important to note that SCOPE should be one of the scopes you specified when delegating authority.
2. Access the API:
Once the OAuth service is built, you use it to retrieve an access token with which you can access the desired resource. Of course, GmailApp service and the Advanced Gmail Service won't be of use here, since you have to access the API using the service you just built. Because of this, the way to access the API will be making the corresponding HTTP request via UrlFetch.
I'm not sure what you want to do exactly, and the exact request would depend on that, but for example, if you wanted to list the messages from the impersonated user, you could do this:
function readInbox() {
var service = getGmailService();
console.log(service.getAccessToken());
if (service.hasAccess()) {
var url = 'https://www.googleapis.com/gmail/v1/users/me/messages';
var response = UrlFetchApp.fetch(url, {
headers: {
Authorization: 'Bearer ' + service.getAccessToken()
}
});
var result = JSON.parse(response.getContentText());
console.log(JSON.stringify(result, null, 2));
}
}
Note:
I'm assuming here that you have already created a Service Account and granted domain-wide authority, and that your issue was just using it in Apps Script.
In Gmail API Reference, check the HTTP request, Parameters and Request body sections corresponding to the API method you want to use, if you need information on how to make the HTTP request (URL to access, HTTP method, request parameters, etc.).
Reference:
OAuth2 for Apps Script
Apps Script OAuth2 > GoogleServiceAccount.gs

Answer 2

You cant use delegation from apps script as apps script doesn't support using service accounts. You would need to make an oauth2 flow and have that user authorize it. Answer provided by #Zig Mandel
On top of what #ZigMandel said: unless this is a google domains or google for work account to my knowledge you cant use service accounts with gmail. you need to use Oauth2. Answer provided by #DalmTo

Answer 3

I don't know if this would solve the problem, but a feature request has been placed on Google Cloud Community and on Google Issue Tracker to enable access to Gmail Apps Script add-ons from delegated mailboxes.
The more upvotes, the more chances Google seriously looks at this issue ;).