I have a small deployment I am working on and I am looking to have a shared mailbox indicator for all desk phones, which are VVX 400s and a handful of VVX 300s. There will be no individual voicemail for any of the extensions for now. The shared mailbox is setup as a virtual extension.
I also want the voicemail button to route to this shared mailbox.
Perhaps it is already solved, but have you try manually adding voicemail info in Mailbox?
Suppose shared mailbox is “1000@device”, and you allocate 1001, 1002, 1003, etc… extensions to Polycom VVX phones, then you can add “1000@device” to Mailbox field (Applications → Extensions → <select VVX’s extensions> → Advanced → Edit Exteions → Mailbox) to all of them.
On Polycom VVX phone side, you can modify Message Center category parameter as in below. (In my case, I am using VVX 601)
When the phone is provisioned with exteions, MWI indicator lit if any messages are in the box, and when mailbox is accessed, “Commedian Mail ~” voice prompt will be played and mailbox extension and PIN will be asked for access.