I think he means Automatic Alternate Routing (AAR) which can be optionaly configured, so when calls using that Voice Mail ports are blocked due to bandwidth issue the call will be rerouted to the PSTN.
In CCM 4.0+ it really doesn't do anything as you need to configure AAR only on the voicemail hunt pilot, with CCM 3.3 and earlier if you wanted to re-route voicemail calls through PSTN when out-of-bandwidth you needed to configure AAR on the ports.
You're brining up a good point, one scenario could be that subscriber A is configured to be notified on phone B at another location when he receives a voicemail, normally the notification will be delivered via a call originating from the voicemail port, now assume that the bandwidth between the voicemail site and the remote branch site is exhausted, AAR (if configured) would kick in and re-route the call. This is just an example, which in real world is unlikely as you usually place the Unity server at the head end site and assign unlimited Location.
If you simply want to preserve Voicemail calling you need to apply AAR group and external voicemail mask to the Hunt Pilot used by the voicemail hunt list/line group.
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The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...