Cc send message list does not work properly

Hello all,

I created a ticket and set User1 and User2 as Cc. For some Comments I want that only User1 must be notified. I order to do that, I accomplished theses tasks:

  1.   I click the link to add comment
  2.   Under Scrips and Recipients --> This message will be sent to ...  -> I checked the checkbox for user2, in order the add User2 to the list of users, who will not be notified.

Now the User2 is existing in the list of people, who will be notified AS WELL AS in the list of people, who will be not notified !!!

If I do the same for User1 all things is working well and User1 is existing ONLY in one list !!!

Why ???

I am using RT 3.8.1

Many Thanks !!!