OWA receives mail but local Outlook client doesn’t

I am having an email problem with one of the users on the network. For some reason last week the user only received new emails from a non-specific variety of senders in their Outlook Web Access mailbox and not their local Outlook client. Note that some of the senders are local and some are not local. I checked the user’s account in Exchange 2003 and found nothing wrong. Anyone ever see this problem before?