Home Computer Amazon Introduces a $30 Mailbox-Sensor Secretly; You’ll Now Receive an Alert When... ComputerSoftware Amazon Introduces a $30 Mailbox-Sensor Secretly; You’ll Now Receive an Alert When Mailbox’s Door is Open By admin - September 27, 2020 93 0 Facebook Twitter Google+ Pinterest WhatsApp Amazon secretly unveils a new Mailbox Sensor. Customers can now pre-order the item starting on Oct. 8.