Every single time I get an email from GoDaddy, I get two of the same one. Doesn't matter if it's an account statement notice, a domain notice, or anything else, always a dupe. This has been happening for literally 2+ years! It is definitely not an issue with ANY other sender and never has been. Only you. I'm not sure where to post this, I don't even know if you have email support, but I didn't want to call and try to get sold something. So move this to the correct place if you must please and tell someone to correct this nonsense, this dupe email thing has been annoying me for a VERY long time.
I should give you more details. I only use POP mail. I do not check it from more than one location. It doesn't matter if I go directly to the web mail or a client, it's the dupe email every time that gets sent to my email provider. My take is that the connection is getting interrupted every single time and it's something server side, as in for whatever reason your server isn't receiving a confirmation of delivery. My opinion is, that if it was recipient side not sending confirmation, then it would certainly be happening with more senders not just you. Again, I have NEVER gotten any dupes from anyone but GoDaddy, and with yours it every time.