Problem: GroupWise requires that all emails contain at least one "TO" recipient when addressing an email. But, I want ALL the recipients to be anonymous.
Solution: You need to create a mailing group (distribution list) in your address book, however, you don't want members of that group to see the addresses of other recipients. You want everyone to be anonymous.
Create a group as you normally would, but instead of adding members as normal recipients (TO:), add everyone as a blind carbon recipient (BC:). Save your group.
Now, whenever you create an email that is to go to the group put the group in the "TO" field. When you send the email, all individual recipients will be in the "BC" field and will only be able to see their own email address.