Use Asterisk as 3rd party Voice Mail for legacy phone system

I am trying to use Asterisk as a 3rd party voice mail on a legacy phone system. The connection is using FXS ports on the Asterisk. All integration is DTMF inband. The long term plan is to use the asterisk for everything. The customer does not have a budget to buy phones yet.

Has anyone done this before?

What file will look at the incomming inband DTMF and allow me to build translations to direct to mail boxes, ETC??


I hope the connection will be via fxo ports , also what is the legacy system ?

For you particular application, you would just need extensions.conf to answer the line and start the voicemail application

exten => s,1,answer
exten => s,n,voicemail(100@default)
exten => s,n,playback(vm-goodbye)
exten => s,n,hangup

and users.conf to define your mailboxes.