AASTRA 4225 for MX-ONE Telephony Switch - Manual (Page 84)

Messages
Dialog 4223 Professional/Dialog 4225 Vision 84
To handle the mailbox
Recorded information on the line tells you the number of new and
stored messages. If you have too many messages stored, you will first
be asked to delete saved messages.
Recorded instructions ask you to press different digits in order to listen
to callers’ messages, record your own greetings, change your password
or exit your mailbox, etc.
The following diagram gives an overview of the mailbox system and
the digits to be used.