You have exceeded your mailbox quota for your account. There are several steps you can take to reduce the size of your inbox for better performance:
- Delete older inbox items. You can do this quickly in the app by setting a custom Swipe motion to delete: Settings > Mail > Swipe Options. With this set, you can easily swipe your way through your inbox to clear it out.
- Empty your Junk email folders. Go directly into your Junk folders and press Delete.
- On Android, you may empty your Junk email folders with one click. Go directly into your Junk folder and press Delete.
- Increase your quota by buying a subscription.