The email connection method is set to run every X hours according to the monthly subscription plan.
If you are subscribed to the Basic plan, then the email will only process every 24 hours and if Enterprise, then it will process every 4 hours while if Pro plan it will process every 6 hours.
To know the waiting period, please refer to the activity log of the feed. If the last process time was 4 pm then the time will start from then.
Until you reach the time, your email will be on queue.