From FFXI Wiki

An item with the Exclusive Exclusive designation are bound solely to your character. You may have multiple exclusive items (e.g. Beastmen's Seal), but you may not sell or trade them to other players. Some exclusive items can be sold to NPCs, although this is uncommon. This is often pairs with the Rare Rare designation, thereby fully binding the item to a character.

An exception to this rule is that some Exclusive items can be sent to either yourself or another character on the same PlayOnline account. This is designated as the "CanSendPOL" flag on multiple item pages throughout the wiki. This was done to help alleviate player's inventories. Many new items are implemented with this flag already on them.