This relates to SOD, Wild Growth EU.
Since today, approaching the Orgrimmar innkeeper while being in line of sight of the apple bob now puts you in combat permanently while you are in Orgrimmar. Additionally, some players are reporting that while in combat, interacting with the mailbox reports addon errors which block the mailbox from opening.
Running out of Orgrimmar into Durotar drops combat, and once you do, the mailbox interaction works again.
This does not happen in Thunder Bluff.
Speculation: There is an invisible NPC linked to the Halloween event that is entering combat with players who approach the apple bob. However, seemingly only in Orgrimmar(?).