I just tested it and I got the email immediately.
I'm thinking it might be because you are using a PartsbyNC.com email address and the email server might be recognizing that it is in charge of those email addresses and that it didn't send the emails and is therefor identifying them as SPAM and not letting them come through.
A solution might be to use a different domain as the FROM address so that your email server won't improperly block the emails. The good news is that it appears your customers would have been getting receipts and the emails are getting sent properly. It is a receiving issue on your email server most likely because of spam settings. You may be able to investigate and get this fixed with your email service provider.... are you using valid FROM email addresses? It might help if you actually register the email addresses you are using.