On page:

http://roundup.sourceforge.net/doc-1.0/customizing.html

it reads:

"automatic registration of users in the e-mail 
gateway... This is the default behaviour in the 
tracker templates that ship with Roundup."

However my new tracker schema.py has the following 
comment:

"# This is disabled by default to stop spam from 
auto-registering users on
# public trackers."

The online docs should be changed to say that 
automatic registration by email is disabled by 
default, but can be enabled to uncommenting the 
appropriate addPermissionToRole in schema.py