A question... what happens if a trunk has it's own voicemail system and a message is left there? A SIP NOTIFY message will get sent from the trunk to i-p-tel PBX indicating that there are messages waiting. But what will i-p-tel do with that message?
I've not tried this but I'm guessing that the message will be ignored. Can anyone confirm?
The more interesting question is what should/could i-p-tel do if it receives that message? Maybe an extension could be setup with "trunk provided voicemail" option so that if i-p-tel receive a message waiting NOTIFY from a trunk, it would pass that on to a designated extension?