Since some people on the mailing lists are asking for this, I decided to release it into the public domain.
Asterisk MWI is an interesting animal. Most people don’t realize that the MWI light is turned on simply by the presence or absence of the msg.txt files in the voicemail user’s directory. Using the method I’m outlining here will allow you to keep the load light on any call servers and have the voicemail server(s) handle notification and voicemail storage. This method is also immediate, since every time a call is made, Asterisk does the processing and sending of the MWI instead of a cron job that’s run every X minutes…