XP Item Bug - 40% Extra Experience (Patreon)

Some quests such as invasion-type world quests or missions from the mission table award a purple "XP" item. This item vanishes as soon as you click on it-it never goes into your inventory, and awards some amount of xp.

Often this item is automatically put into your bags, as for example with a demon invasion quest, and the xp from the item is automatically awarded.

However, if you fill up your bags, for example breaking up stacks of an item with shift+click to cover all inventory slots, then the item will be sent to your mail for you to receive at will. 

Why is this important? Because it allows you to receive the item at any time and any place and maximize the value of any xp bonuses that may be in effect.

 For example my rogue stacked several of these xp items from demon invasions at level 98. I then used my garrison hearthstone, bought a garrison experience potion and went to Spires of Arak, where you have an outpost which can award 20% extra zone xp, and a convenient mailbox. This allowed me to get 40% more xp than I would had I received the award immediately in the Broken Isles. 

This is clearly an unintended effect Blizzard have created since the Spires of Arak buff is clearly only meant to be active from activities that take place within the zone. 

I have not tested this yet as I do not have a level appropriate demon hunter, but this bug very likely works with the experience dupe I mentioned here:  https://www.patreon.com/posts/26514870 

making it a very powerful technique. 

It also seems likely that any quests that can be remotely completed could also be exploited in much the same way.