can't open mail box with squirel mail web client

Hi,

I've got a Sendmail server, one of the accounts on it has about 1500 email
in the inbox. I can access the inbox via Email client such as Outlook. I
want to be able to access this mail box using the squirel mail but for some
reason I can login into the squirel mail but it won't show the content of
the inbox even on the mail server itself. Does anyone have any idea how to
fix this?

Thanks