I found a bug in Catch-All configuration. I have a domain that configured the Catch-All to an Alias. After that, delete the Alias and Smartermail continue to received messages. When try to delivery to the alias that doesn't exists make bounce. This can be considered a backscatterer problem.
1) create a domain;
2) create an alias;
3) configure the domain catch-all to this alias;
4) remove the alias;
5) don't set again the catch-all to none (don't change the configuration).
If you try to send any email to invalid address for this domain Smartermail received that with no problem and make a bounce after in delivery process.