You may check your inbox storage by logging in your account thru GoDaddy Webmail.
Below is the link.
Checked it per link and showed 4% used. Not really sure how that is as no e-mails were present in any folder.
But on my IPhone my godaddy email shows 100% full with nothing in any of the folders?
Called customer service this morning and they did diagnostics and really didn't see any issues. All my platforms seem to be right at the present time. The inconsistencies are a concern. The rep was helpful but didn't seem real up on my concerns. They just try to sell more stuff.
Maybe you can do some troubleshooting by sending test email to your email using other mail platform.
I.E. Google, Yahoo, etc..
Check if you can receive your test email.