Autocreated users, howto disable this

Morning

I know this has been asked before but not real solution was given.

I would really like only registered users to be able to use our RT
system. But sometimes odd emails hit the rt address and then a new user
is created for that email address.
This is really irritating and I would like to disable this autocreate
feature. The best scenario would be if rt replies with instructions on
how to contact someone etc.

Thanks in advance

Gert Burger

TechTeam
Computer Science Department
University of Pretoria