Whenever I use my Mac outside and connect to the internet via my dongle, or a shared wifi, Outlook freezes and I constantly get this alert:

'Mail could not be received at this time.  The server for account "Gmail" returned the error "[ALERT] Too many simultaneous connections. (Failure)." Your username/password or security settings may be incorrect. Would you like to try re-entering your password?'

I re-enter my password again and again in order to unfreeze Outlook, but still the alert keeps coming back, which renders Outlook  unusable when connected.  

I would be grateful for advice on how to disable this alert, or configure so that it only comes up every few minutes instead of every few seconds.

For info, current Outlook settings in Accounts/Advanced/Server are: 'sync all  IMAP folders every 10 minutes' and 'refresh server connection after 20 minutes'.