1. Press the Voice Mailbox button on the phone (marked with envelope icon)
2. Press 0 (zero) and follow prompts to record and save greeting.
Important Note When Recording Mailbox Greetings: It's useful to record both an "Unavailable Greeting" and a "Busy Greeting". This way, if you reject a call or don't answer a call while on the phone, callers will be sent to a "Busy Greeting". If a call goes unanswered while your not on the phone, and it has not been rejected, callers will be sent to an "Unavailable Greeting".