I have run 2 dungeons and they both dropped fairly significant upgrades for my character but I left the dungeon before they reached my bags, they did no appear in my mail or in my bags later
## WoW Classic Era and Classic Progression
Unlooted items in WoW Classic Era and Classic Progression realms are not sent to your mailbox. Items that aren’t looted will remain on the corpse until it despawns. Customer Support does not recover unlooted items.
If you want to see this changed submit a suggestion ingame or recreate the topic at a non-support feedback forum!