Lewis011, wondering if you ever figured out the magically fix. I am having the same exact problem. Everything mentioned here has been tried. April 12th was the last day I received mail in my Inbox (Go Daddy) account. I switched to an IMAP account the end of March and got everything set up on my Mac and iPhone with the intention of adding an iPad shortly. This happened and now I don't know!
I have deleted the account numerous times. Not only deleted the account but then restarted and the added it back in. I have been working with an Apple advisor and we have tried various port settings which I had also tried before contacting Apple for support. I can send mail from the account but cannot recieve in the Inbox.
Here's the kicker, on the Mac, I can move an email from the Inbox into one of my various folders I have made. Then go to my iPhone and go to that folder and there is the email. So I can see recent emails if I move them into folders but I cannot see those same emails in the Inbox.
I would be so grateful for any extra advise from anyone.
PS - iPhone 4S Version 5.1