title: Google OAuth 2.0 Service Account vs Administrator Account
body: <p>This question is specific to google business/education accounts. I couldn't find any documentation on this. 
  I have a server application that needs to access google mail inbox and check the read/delete status of certain messages based on filters. I need to do this without requesting user authorization or any involvement of the user.
  Should I use an administrator account or a service account and what's the difference between the 2? 
  Are there any limitations on how many mailboxes can be accessed and how often can they be accessed by an administrator account or service account?
  For eg: IF I need to check 5000 mailboxes based on a filter, how frequently can I do this using an admin account or service account.</p>