See our pricing page for daily and hourly email sending limits: https://ozcart.com/pricing
If you are sending a large number of emails (newsletter, etc.), you will need to take this into account. You can also sign up for a reliable newsletter system (Mailchimp, Elastic Email, SendGrid, etc.).
Some email programmes allow you to set how many emails are sent every hour. You may use that to your advantage to limit your sending to a bit less than the max per hour mentioned on our pricing page.