“You’re about to throw away this message without sending it” associated with a frozen window, BUT, e-mail out actually does get sent.

Stated another way, when I click on 'send' the action dots begin spinning and do not stop.  The usual message stating my e mail has been sent does not appear.  The now spinning dots spin, nothing else appears past that point.  When I click on a return to incoming e mail page, the "You're about to throw away this message without sending it" appears.  When I check the "sent" box, the e mail in question is listed as sent and the recipient addressee receives the message.