We had a UC520 customer who wanted the MWI to appear on the phone whenever there is voicemail in a general delivery mailbox associated with a shared line. They were using Cisco 7931G phones at their customer site, and the envelope is difficult to see on the Cisco 7931G phones (which have a small screen). We were able to get the customer to understand that the envelope would appear and that the MWI light would appear when a message was delivered to the GDM.
Here is what the Cisco Unity Express CLI Voice Mail and Auto Attendant Administrator Guide states regarding General Delivery Mailboxes:
When a caller leaves a message in this mailbox, no MWI is turned on.
On Cisco SPA525G phones, if there is a voicemail message in a GDM associated with a shared line, both the MWI light and the envelope will appear. This behavior is different from the 7900 series phones or the behavior described in the CUE documentation, but is the behavior that some of our UC520 customers want.
On the Linksys One platform, if there was a voicemail message in a group mailbox, the MWI light would show up on the phones in the group.
This functionality really should be added to the phone loads for the Cisco 7900 series phones. The problem is not in IOS, CME, or CUE code because the SPA525G has the desired functionality. There should really be an option to choose either the old behavior (where the MWI light does not come on for messages in the GDM) or the new behavior (where the MWI light does come on for messages in the GDM). This option to control this behavior needs to be available from both CCA and CLI.
I believe that the SPA525G MWI behavior is correct, even though it is not consistent with that of the 7900 series phones or the behavior described in the CUE Administrator Guide, because Linksys One has similar MWI behavior.