Undelivered has assured a customer that storing an unsent letter will not alert the person it was written to. The recipient will not even learn that the letter exists.
Owners can give letters private labels, come back to them or order their destruction. The archive does not analyse feelings or suggest a good time to send them.
Slow Post can deliver a letter if its owner decides to send it. Perennial can arrange for a human to look after it over a longer period. Storing a letter gives neither company permission to contact anyone.
One customer said her letter was easier to keep once it stopped asking to be sent. The recipient remains unaware of the improvement.