The only way to send non-account bound items across factions is with the help of a friend.
Hereof, can you send items between Horde and Alliance? Neutral Auction Houses are as follows : Gadgetzan, Tanaris Desert Booty Bay in Stranglethorn and Everlook in Winterspring. Go to a neutral AH (Auction House) and put a rubbish item with 24 gold buyout.
Log in to the character to whom you want to transfer. Transferring from a Horde Character to an Alliance Character.
