Our SPA504G phones are provisioned to receive MWI from our SIP provider. For the most part MWI works fine, except the red light is on and a little envelope is shown next to the extension key every time the phone reboots - voice mail pending or not. How can we determine if our service provider indicates MWI or if the phone invents its MW indication? Are there any configuration options besides Message_Waiting_N_ and Mailbox_ID_N_ to control the behavior of the MWI?
Please get a network trace. Depending on the SP, the MWI may come differently depending on the messaging used. Get the traces and send it over so that I can check whether the network is indicating any pending message.