Email sent during iCloud storage overage and retrieved after upgrade

So the other day, my iCloud storage ran out but I did try to send an email from my iCloud mail and I'm unsure if it actually did go through. Only after sending the email I upgraded my iCloud storage and when I did so my email was no longer in the sent folder, but after a day or two that email went back to the sent folder, and now I'm extremely confused whether to resend that email to the recipient or not.

[Re-Titled by Moderator]