How do I set up my Grandstream Shared General Voicemail Box?

Create a New Extension:

1. Log into the UCM Web GUI.
2. Navigate to Extension/Trunk → Extensions.
3. Add a new SIP extension (e.g., 3000) and name it "General Mailbox".
4. Ensure Enable Local Voicemail is checked in the Basic Settings for this new extension.
5. Route Incoming Calls:
6. For the specific line (Inbound Route) or Ring Group, set the Default Destination to "Extension" and select your new "General Mailbox" extension.

Configure Phone Monitoring:
To allow multiple users to see and access this general mailbox, add a Virtual Multi-Purpose Key (VMPK) to their phones.
Set the Mode to "Voicemail" and the Value to the general extension number (e.g., 3000).
In the phone's configuration, you can set the access code to *98 followed by the extension number to check it directly. 

Recording the Greeting
From a Phone: Dial *98, enter the general extension number (e.g., 3000), and enter the PIN.
Navigation: Press 0 for Mailbox Options, then press 1 to record the "Unavailable" message (the main greeting callers will hear).
Upload via GUI: Alternatively, record a file (8000Hz, 16-bit, Mono PCM) and upload it directly under Call Features → Voicemail → Voicemail. 

Quick Feature Codes
*97: Access your own extension's mailbox.
*98: Access any extension's mailbox (requires the extension number and PIN