Outlook not receiving email, but sends email?

[JonnySki]

I have outlook express and it has always been fine, however now it sends email, but it does not receive it over the last few days. I get the messages on my iPhone just don't come through to outlook. Its not POP3 its IMAP. I have rung the company who host the website with which the email is through, 123 reg, and we have been through all the settings and they are all correct.... so why does email still not come through to my outlook when it always used too... help??