Since NetHunt CRM lives inside Gmail we are bound to its sending mail limits.
You can find its daily limitations here, as it all depends on your G Suite account.
The limits are applied for 24 hour period. In case you send out a campaign at 11 pm, the quota will not reset at midnight. It will reset after 24 hours, meaning at 11 pm next day.
In order to avoid Google limitations, you can connect a custom SMTP and send out more emails.
Also you can use dedicated servers of NetHunt whenever you send out an email campaigns. Note that this option available only for paid subscriptions.