Outlook "Send As..." Simulator
Try to do these steps:
1. Ask your Exchange admin to create 2 custom recipients accordingly your Inet accounts and to give your account Send As right (CR properties -> Permissions) for each;
2. In OL copy these CR to your Personal address book (PAB);
3. Ask your Exchange admin to hide these CR from GAL;
4. Make sure you have Microsoft Exchange transport first in the list (Tools -> Services -> Delivery in my OL98)
5. Make From field to be permanent on your New mail form. Then try to set from field as one of new addresses you just created in PAB.
I have tested it with Exchange 5.5 (SP2) + OL98.
Feel free to send me your comments and criticism.
Send comments to firstname.lastname@example.org