# Configure an Overflow Mailbox

You can use an overflow mailbox to accept messages when a primary mailbox is full.

To configure an overflow mailbox:

1. Customize an FCOS to include feature bit 189 (Rotate on Full Mailbox).

2. Create a standard mailbox that will be the overflow mailbox, or use an existing standard mailbox and assign the customized FCOS.

3. Create Distribution List 1 for the primary mailbox, and add the overflow mailbox as the member. You can add more than one mailbox to the list and the server uses each one as an overflow mailbox when the previous overflow mailbox fills up.

When a new message is received by a full mailbox, it is routed to the first available mailbox in the full mailbox’s Distribution List 1 (the overflow mailbox).