Outlook Express os OS 9 times out receiving

[warchyld]

I have a person using several OS 9 machines with Outlook Express on our network. It was working fine up until last week when they stopped receiving mail. They can send fine, but receiving just times out. Their mail provider tells them they didn't change anything. I can set up the same accounts on a Windows machine, or my OSX machine (with the OSX mail client) and the accounts work fine. It's just the OS9 machines that are timing out.
I tried briefly opening up our firewall to one of his machines, but it still timed out.

Any ideas?

Thanks