If you want to limit when in the day you want to start and stop sending SMS messages and emails to your contacts, go to:
Left Side Menu Bar > Settings > under General section > General Settings
Under Additional Business Settings page, you'll find "When can scheduled emails and SMS messages be sent?". After selecting your preferred schedule, scroll down at the very bottom and click "Save".
This will be a great way to prevent emails or sms messages and undesirable times like midnight or early in the morning.