A swing away or pivotable mailbox support includes a lower post anchored in the ground and pivotally connected to an upper post having a horizontally projecting mailbox support arm. The upper post is pivotally movable in response to horizontal loads applied to the support arm. Adjacent connecting ends of the posts have aligned centrally located mounting bores for receipt of a mounting shaft. A bearing and detent assembly is mounted to the connecting ends of the posts to provide support and relative rotational movement between detent-engaged stable rotational positions. A kit including a bearing and detent assembly and a shaft is also provided for converting a stationary mailbox support to a swing away or pivotable support in accordance with the invention.