Thank you for your response. I will try to better explain.
I log on to the workstation as a standard user and run the mail using GroupWise administrator user (User1). I choose the proxy account (User2 - standard user groupwise) and I try to answer the mail as User1. So I click on the proxy account, choose the account User2 then choose reply. I click on the button "from" which opens a menu where I have to choose "Account" or "Novell GroupWise". When I choose "Novell GroupWise" in the user changes "from" User2 to User1.
As I try to do the same as a normal user groupwise, the menu does not appear when I click "from". I checked on the GroupWise 2014 and everything is fine.

My system is Groupwise 2012 Sp2