If you get the following message when you try to connect your Google account to sync email and/or sync your Google calendar, you might need to change your settings in your Google account.

Sometimes Google force you as a user to allow third-party apps like Salesbox to get access to you different apps inside your Google account. 

To understand how you change these settings please go to this Google support page: https://support.google.com/accounts/answer/3466521?hl=en

In this article Google describe how to change the rights for third-party apps.