Outlook 97 won’t check for new messages

I an running Outlook 97 on Win 98 SE. I have a 56k dialup connection to my ISP. While I’m on the net I expect Outlook to check for new mail every X minutes. In the Options dialog box under the Internet E-mail tab I have the box checked and I’ve set the interval to 10 mins…But it won’t check for new mail unless I do it manually. Any ideas?