Hello Steven,
If I understand your concern here correctly, what’s happening is that when you forward an email from your email system a case not created right?
Just to make sure that we are on the same page, I did some testing. I went to my outlook, sent a new email to the email address of my test account for email case capture and the case was indeed created.
Then I opened an existing email in outlook and clicked on Forward pasted the email address in the To field then sent.
It took a few minutes before the case was created but it was created on my test account. Did I perform the correct steps to reproduce?