Just a quick thought, using an external mailer is possible:

http://wiki.freeswitch.org/wiki/Mod_...email_to_Email

The API feature is pretty rich which, as a developer, got me pretty excited to see the possibilities (but yes, it's like opening a pandora box for a widely deployed service like VOIPo).

Most exciting of them, from the FAQ section:
Do I need a text-to-speech engine installed?

No, it will work with sound files or a text-to-speech engine.