Panasonic KX-NS1000 User Manual page 34

3-3 Basic Settings : Creating Mailboxes (5)
Creating multiple mailboxes at once (UM configuration)
2
Set the mailbox parameters
Check "Use the same number for Mailbox and Extension"
to assign each mailbox to the same number extension.
Specify the range of mailboxes
to add in From and To.
You can edit the default settings to be used
for new mailboxes.