There are two common uses for mailbox buttons. The first is to allow one extension to have direct access to multiple mailbox buttons, such as an attendant with remote workers or when multiple people share the same telephone. The other is to allow multiple extensions to have access to a specific mailbox, such as a group or department using the same mailbox. The feature code is F66 + MBX.

The 45P will always answer with the auto attendant greeting, unless the CO Lines are marked as “Private To:”, and has a fix 10 second time out after the main greeting finishes plays. Therefore, it is better to have the caller dial the extension or department number, otherwise they will be waiting for 10 seconds and then get transferred to an extension or mailbox.