MWI not working

[kmccracken]

I'm using Asterisk v11.2.1, and several Yealink T38G's. I'm using the phone's mac address as it's sip account name. I dial *97 to get to the voicemail system. I haven't been able to get the Message Waiting Indicator to work. I'm not sure what settings need to be made. Here's what I have so far:

In sip.conf, I have:
[general]
mwi_from=asterisk
[template](!)
type=friend
context=internal
host=dynamic
disallow=all
allow=ulaw
allow=g729
allowsubscribe=yes
dtmfmode=rfc2833
sectret=<removed>
callcounter=yes
subscribecontext=extensions

[0015653fabcd](template)
mailbox=111

In my voicemail.conf file:
pollmailboxes=yes
[mycompany]
111 => 0000,Test User

On the T38, I have:
Subscribe for MWI=enabled
SubscribeMWIToVM=enabled

Obviously I'm missing something somewhere. Is there a guide that shows what settings should be set on the phone & in Asterisk to get the MWI to work? Or could someone provide some direction?

I've seen reference to different settings in Account | Basic | "Voice Mail". I'm not sure if it should be *97 (which is what I use to dial the voicemail server), or 111 (which is the extension), or 0015653fabcd (the mac address of the given phone). Also, I've tried enabling "Use user=phone" under Account | Advanced on the T38, but none of those got this working.

Any help will be much appreciated.
Thank you.