Any passcode less than 4 digits should not be used. Any one who knows or can guess a passcode for a voicemail box, can access the voicemail box. Also, a voicemail box is accessible from any phone, inside the campus or outside. Consider the mischief that can be created by someone using your voicemail box to send messages. At anytime during the greeting, the caller can press 1 to skip the remainder of the greeting and begin recording a message.
Voicemail is intended to be for short term storage of messages.
Messages more than seven days old will be automatically removed by the voicemail equipment. However, you should understand its interaction with the voicemail equipment. The voicemail equipment will answer a call after five rings. If your answering machine picks up a call in fewer rings, then it will respond to the call before the voicemail equipment. On the other hand, if your answering machine is set to respond after more than five rings, then the voicemail equipment will pick up call first.