Yes. To prevent spam, only our paid plans allow you to send more than 5 emails/SMS at a time. Depending on your plan you will have different limits.  Please refer to our plans to see the details.

https://www.duplie.com/find/Pricing.jsp

If you use your own mail provider, there may also be limitations on their side.  Some providers like gmail limit the amount that can be sent per day. You may want to check with your provider to see what the limit is. From Duplie's side, we will try to send it, and if it fails, we'll try again in an hour. We'll do that for 5 days, and then we give up.