Outlook not Downloading email until two days after it is received on server

[creeks5]

One of the computers at our church is having trouble getting their email from our server using Outlook.  New emails typically don't arrive on the local computer until about 48 hours later.  Some are apparently filtered out and the user doesn't see these at all.  The emails are there when the user accesses the email account with the web interface. I assume this is an issue with Outlook since the emails are arriving on the server in a timely manner. Does anyone know what could be causing this issue?  We're not having this issue with any of our other email accounts, even those using Outlook.

[MrPhil]

I don't use Outlook, but can think of a couple obvious things to check. Is the PC in question continuously "on" and connected to the Internet, or is it off most of the time? Especially if it's often off, how often is Outlook configured to check in with its mail server and see what's there? If you manually order Outlook to fetch its mail (I presume that can be done), does it all show up immediately? Is the Internet connection very slow or unreliable?

[creeks5]

The computer is off when no one is in that office but Outlook is configured to check for mail automatically every few minutes when the computer is on.  Even when Outlook is told to check for new mail manually the new stuff doesn't show up for a few days even though the new mail is available through the web interface..