This page of our game guide to Control - AWE contains a detailed description of the Return to Sender side mission. By reading our guide you can find out where to find the chain letter and the photocopier, as well as where to deliver copies of the letters.
How to unlock the mission: You need to find a chain letter in the location of Shifted Offices. It lies on a shelf in front of tubes used to send correspondence, not far from one of the checkpoints.
Take the letter to the Operations Center. On the ground floor of a large room, find the photocopier shown in the picture. Interact with it several times to create several copies of the letter.
Copies of the letter must be delivered to three different locations:
- Abandoned Offices
- Observation Deck
- Utility Corridor
In each of these locations, find the tubes used to send correspondence. You have to interact with them.
After sending 3 chain letters, return to the Shifted Offices where you started this quest. You will find the object of power near a checkpoint - as shown in the picture. Follow the tubes on the ceiling and the wall to reach it - it is a levitating mailbox. Interact with it to clean it up. That's how you will end the quest.