Email not sending in Agent Desktop or Web Agent

Summary

Emails are not sending to customer when using send button

Content

Hi, in the Agent Desktop and Web Agent we can't send an email response to the customer using the Send button (or send on save checkbox).  After sending and saving it shows the message response entry to customer in the incident and all indications that it was sent after saving but it does not Send it.

However, if I use the forward button a forwarding dialog pops up and after typing in the customer email address it does forward the message to the customer.

Does anyone know why the message responses are not sending out to customer?  The mailboxes must be set up ok as the forward works fine.  I attached some images as references.