Helping the Cenarion Post (Alliance)

Cenarion Post is at 15, 52 on the map. This is somewhat northeast of the Ruins of Sha'naar.

This quest becomes unavailable if you do Demonic Contamination.

There's lots of quests that say "go see <npc name>, they have a quest for you." Most of these aren't necessary, though, as you can get the followon without doing the "go see the person." So once you do Demonic Contamination, you are no longer eligable for Helping the Cenarion Post, 'cause the quest they are telling you to do is no longer available to you. It's like the quest in the level ~5 town when you hit level 10/12 to go see your trainer in the nearest big city to get your class quest. The trainer in the big city will give you your class quest even if you never see the local level ~5