This question is not about wormhole direction as covered by Entering an Active Wormhole from the Destination. This scenario is about an outgoing gate (dial out) where the person/ship that dialed enters the event horizon from the other side of the gate.
When people dial a gate, they generally enter from the 'front' of the Stargate. On most planets, the front of the gate is the end that faces toward the DHD. It is the side that has the 'kawoosh' splash out effect.
Even when space gates were seen in Atlantis, we get treated to a scene where some Wraith Darts are guarding a gate, but they only defend one side:
What happens if a person or object entered from the 'back' of an active, outbound gate?