Thanks for the feedback, @takayukister ! It may be that this is the expected behavior, but the log should at least note that the potential second email was never sent in the first place. If the second email—that is, the confirmation email—contains important information for the recipient, I see no reason why this functionality shouldn’t be available.
The information in the email is now gone and cannot be recovered or resubmitted. That should not be “expected behavior”—quite the opposite.
