Automate Gmail forwarding using API: Troubleshooting permission issues

Other Questions Gmail
1

Hey everyone, I’m trying to set up automatic email forwarding using the Gmail API. I’ve got most of the setup done, but I’m hitting a roadblock with permissions. Here’s what I’ve done so far:

  1. Created the necessary files (storage, credentials, etc.)
  2. Set up the SCOPES for sending mail
  3. Tried to create a forwarding address

But when I run my code, I get this error:

HttpError 403: Insufficient Permission

I’ve already given the sending mail permission, but it’s not working. I can’t find a specific scope for forwarding messages in the docs. Do I need to upgrade to G Suite for this to work?

Here’s a simplified version of what I’m trying to do:

def setup_forwarding():
    SCOPES = 'https://www.googleapis.com/auth/gmail.modify'
    creds = get_credentials()
    gmail_service = build_gmail_service(creds)

    forward_to = {'forwardingEmail': '[email protected]'}
    result = gmail_service.users().settings().forwardingAddresses().create(
        userId='me', body=forward_to).execute()

    if result['verificationStatus'] == 'accepted':
        set_forwarding_settings(gmail_service, result['forwardingEmail'])

setup_forwarding()

Am I on the right track here? Any ideas on how to fix the permission issue? Thanks for any help!

2

I’ve dealt with similar issues when working with the Gmail API. From my experience, the ‘https://www.googleapis.com/auth/gmail.modify’ scope should be sufficient for creating forwarding addresses. However, there’s a catch - Google often requires additional verification for forwarding setup to prevent abuse.

Have you enabled the Gmail API in your Google Cloud Console project? Sometimes, the error you’re seeing can occur if the API isn’t properly enabled.

Also, make sure you’re using a Google Workspace (formerly G Suite) account. Personal Gmail accounts have limitations on API-based forwarding setup.

If you’ve covered these bases, try adding the ‘https://www.googleapis.com/auth/gmail.settings.basic’ scope. This explicitly grants access to manage mailbox settings.

Lastly, double-check that your credentials are up-to-date and that you’re authenticating with the correct account. Stale or incorrect credentials can sometimes lead to permission errors.

If none of these solve the issue, you might need to reach out to Google Support or consider using their official SDKs, which can sometimes handle authentication more smoothly.

3

I’ve encountered similar challenges with the Gmail API. One often overlooked aspect is the OAuth consent screen configuration. Ensure you’ve properly set up the OAuth consent screen in the Google Cloud Console, including adding the necessary scopes.

Another point to consider is the type of Google account you’re using. Some API features are restricted for consumer Gmail accounts and require a Workspace account.

Have you verified that your application has been authorized by the account owner? Sometimes, the initial authorization doesn’t stick, leading to permission errors.

If you’re still stuck, try using the Gmail API explorer tool. It can help pinpoint where exactly the permission issue is occurring and what specific permissions are missing.

Lastly, if all else fails, consider implementing a workaround using IMAP/SMTP instead of the API. While not as elegant, it can be a viable alternative for forwarding emails programmatically.

4

yo, i had similar probs with gmail api. make sure u got the right scopes, like ‘https://www.googleapis.com/auth/gmail.settings.sharing’ for forwarding. also, check if ur using a workspace account cuz personal ones have limits. if that dont work, try refreshing ur credentials or use the API explorer to debug. good luck man!