Gmail API Throttling

As a Gmail user, you are able to install apps that integrate with your Gmail via Gmail's API. This is how Vocus.io and other apps are able to interact with your Gmail account. To limit abuse, Gmail limits the number of API calls an app can make to their server. 

If you are seeing an "Gmail API Throttling" error, this means that one of your apps is consuming all of your Gmail API limits. You need to uninstall/block that app or wait until it is done syncing.

How do I know which app?

Tough question, but here are two methods:

• Review Google's Connected Apps list. Remove apps that you do not need them anymore, especially those with access to Gmail/G Suite.
• Review "Last Account Activity" screen. This is found at the bottom right of your Gmail, and it lists the IPs of the machines that access your Gmail. It's easy to distinguish Vocus.io machines (paste the IP address in the toolbar and it will take you to the landing page). If you see other IPs, especially those with frequent access, then those are likely the culprit.