When I first installed billets, things were going fine. However when I started to try to use some the of the advanced features, like submit ticket by email, I started getting 5 and 6 new tickets for each ticket submitted. Which means each time someone submitted a ticket I was getting 4 or 5 other tickets with just garbage all related to that single ticket. So if 5 tickets were actually submitted I would get 25 other tickets with just junk in them that I would have to go in and delete. I contacted support and they were extremely, mind numbingly slow. I would send support screen shots and a full detailed outline of what my issues were and I would get back 1 line reply's like "did you turn the extension on" or "change your email address." So while the concept of this product is great the actual results and the support of this product is much to be desired. I would look at other ticketing systems before I would use this one.
Unfortunately email problems are often caused by server (or Joomla) configuration issues.
In the course of trying to resolve an issue we look for the most obvious (and sometimes very basic) issues first (like 'did you check this setting'). In this case we did offer to take a look at the user's site to try to help track this issue down directly.