Why is my sub-user getting "oops reached your limit" when using the reply feature?

One of my subusers is getting an "oops reached your limit" message when clicking "reply" to e-mail a form submitter while viewing the form submission. 

I do not get the same error when logged in on my account. 

Your sub-user is considered as a free account. Free accounts have the limit of 20 emails sent per hour so the solution is  to wait another hour to send the rest of emails using the submission area reply-to system. Paid accounts can send up to 100 emails per hour.

Hope this helps. Thank you.