Unlimited Inventory Space

Thanks to www.hiddenstuff.com for the info!

Your Mailbox can be used to store inventory items, to place item in your mailbox simply put it in the Auction House and cancel auction straight away. Item will be placed in mailbox for 29days.
Dont forget to grab the item and redo the process again after 29days or else it will expired.

ps. make sure you use the 2hour auction so it doesnt cost you too much deposit