If you've received an email notification letting you know that your sync process has halted due to too many items syncing, you can adjust your settings.
Adjust Google Sync settings on Apple iOS mobile devices
- On the device, tap Settings.
- Tap Passwords & Accounts.
- Tap your account.
- Adjust Mail Days to Sync by choosing fewer days. For example, if your previous setting was No limit, choose instead 1 month.
- Tap your account again.
- Tap Done.
Syncing fewer items will make the sync process run more smoothly. This adjustment applies only to email sync and calendar sync.