Hi Chris,
There is no specific guideline with respect to this case explicitly in my information except mentioned by Martin as below;
Regulations of the Telecom Regulatory Authority of India (TRAI) require that voice traffic over the enterprise data network and the Public Switched Telephone Network (PSTN) must be strictly separated and no mixing of calls between the two networks can occur for the purpose of toll bypass.
Here, 'For the purpose of toll bypass' is a big statement. Laws and regulations can never consider use cases in mind, they are made for specific purpose. Here, one purpose is clearly mentioned in guidelines viz 'Toll Bypass', there is one more purpose which is not mentioned anywhere and that is 'Security'. Let's leave security aside for a time being.
Each and every person can have different opinion when seeing and defining the definition of 'Toll Bypass'.
I won't completely disagree with you when you consider voicemail server as internal and hence can be located anywhere. But if I was in place of regulating officer, this is a serious toll bypass for me as in this case we are taking VoIP call from India to another country without paying any toll to local operator, no matter call is being connected to machine or human. No matter where the location of voicemail server is, it could be in Singapore or USA, local operator would expect this call to take through PSTN from India and then connect to voicemail irrespective of the location of voicemail server then.
When dealing with regulations, it's always good to either get confirmation from respective authority in case of any doubt or play safe game.
https://supportforums.cisco.com/blog/12539601/trai-india-regulations-voipip-telephony
- Vivek
