Did you ever try to set up some manual entries in the /etc/aliases table, e.g. to create an abuse e-mail and forward it to a user-account? No? Well then you never gotten into this problem: 

The /etc/aliases table is periodically overwritten by Confixx, inserting only entries Confixx itself knows. 

The solution is simple but only once you know it. In your Confixx-folder (where all your Confixx scripts are, this is usually /root/confixx) there is a file called "aliases_header". This contents of this file will be inserted at the top of /etc/aliases when this one is being recreated. So to add manual entries into /etc/aliases you need to save them like this:

# cat /root/confixx/safe/aliases_header
# See man 5 aliases for format
postmaster:    root
abuse:          someuser