Christmas Gifts from Dursleys

[spinelli372003]

No: HPFGUIDX 77122

Please bear with me here.  This is my first totally new post.  I 
wondered if anyone else had noticed that the Dursleys had sent things 
to Harry at Hogwarts.  In GOF when he opens his gifts he gets "a 
tissue an all time low" from the Dursleys.  So my question is how did 
it get to Hogwarts?  We know the muggle mail does not go to Hogwarts 
as it is unplottable.   So does Petunia use the owl mail to get it to 
him?  Which brings up a whole new subject of how much does she 
actually know about the Wizerding World?   
Sherry