Yes. To prevent spam, only our paid plans allow you to send more than 20 invites at a time. If you are on a paid plan, then we'll send out as many emails and/or invites as you want.
If you use your own mail provider, there may 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.