Send Command Won’t Use Outlook

Office 97, Outlook 98 and IE 5.5 installed on Win98 2d Edition. Using the Send command or routing slip from Excel or Word brings up a P.O. Login screen although we use Outlook 98 with Exchange 5.5. The login displays whether Outlook is open or not. There are no problems sending and receiving messages directly from Outlook. I have tried uninstalling and reinstalling Outlook. I have tried deleting and recreating the Outlook profile. Why is the Send command looking for a different non-existent mail service and how can it be corrected? Thank you for your assistance.