Error 401: ‘Unauthorized’ is encountered when a server or API request lacks a valid API key, or the provided key is incorrect. This error code signifies authentication failure, typically due to an issue with the API key used to access secure web resources or APIs.
Resolving the Error – Solution
To resolve this error, first verify that your API key is entered correctly. If the key is expired, obtain a new key from your mailer service API provider. If you’re using an SMTP plugin, like Easy WP SMTP, ensure that it has been configured with the updated API key.