Last time I used that was about a year ago. What was wrong with it was that documentation how to set it up was missing and it is really hard to debug. E.g. as far as I remember when the system receives an email it can't deal with for one reason or another it just deletes it silently without logging any error or warning.
And there is simply unimplemented (and possibly hard to implement) functionality like authentication via email and avoiding out-of-office-autoreply loops.