All mail is delivered to the Porters' Lodge and directed to your Pigeon Hole by the Porters.
Your "Pigeon Hole" is one of the small shelves among those outside the Porters' Lodge in Gatehouse Court. It will have your name under it.
When an item is too large for your Pigeon Hole, you will instead receive a slip directing you to the Porters' Lodge, where the item will be kept until you retrieve it.
When an item requires a signature, you will receive a slip directing you to the Porters' Lodge, where the item will be kept until you retrieve and sign for it.
During the vacation, mail arriving at the College for you will be forwarded to your home address (unless you ask for this not to happen). Additionally, when you leave the College your mail will continue to be forwarded to your address for around 3 months.