My machine auto dials when an HTML email is opened and also ignores the disconnect after XXX minutes check box. I don't know whether it is Outlook 2000, IE6 or XP that is causing the problem. Outlook keeps unchecking "Work Offline" no matter how often I check it. I have tried settings from 5 minutes to 1 hour in the disconnect box but the modem (ISDN) just ignores the setting.
I am not 100% sure but I think that this problem only arose after installing XP SR1 or one of the IE security updates.