According to the notes for the event it was stated they could be exchanged.
5 Christmas Gift Boxes: A Christmas Gift Box to celebrate the holiday season. Contains 1 Christmas Cake and 1 Christmas Candle. Can be exchanged, cannot be dropped, sold, or destroyed. Any unopened Christmas Gift Boxes will be removed after 3 months.
When I check the toon i have holding mine the Christmas Gift Box now states that they may not be exchanged, dropped or destroyed.
Is this something that will be fixed or is it carved in stone?
It was a typo, Sace mentioned that before. They just can't be destroyed, dropped or registered at private shop. Cannot remember if they are tradeable, but sure are mailable.
I just now was able to both mail and trade (Exchange button in Actions menu) a box from one non-GM character to another and back, both worked fine.
Remember, only the Christmas Gift Boxes can be exchanged (the white box with the yellow ribbon), not the Santa Hat Set box, nor any of the items inside each of these boxes.
If you try mailing it does it show up in the item list? Cause I had the same problem with 1 char. I tried to sent it, but it did show up in the list but I couldnt select it. I relogged which fixed it.