Unable to receive emails from specific external senders, due to spam classification.
- Admin console
- Spam filter settings
- User with administrator privileges
- Sign in to the Admin console.
- Navigate to Apps > Google Workspace > Gmail > Spam, Phishing and Malware
- Select an OU.
- Scroll to Spam.
- Click on the Edit button > Create or edit > Edit.
- Remove the blue button on the Require sender authentication setting.
- Save changes.
For further information check this article
The approved sender's list still requires authentication to the sender.