There are two places to set the "From" email address for emails originating with the site, depending on which address you want to set ("reply-to" or "from"). First, check to make sure that the principal contact is set on Journal Setup, page 1. Then, if that doesn't do what you're looking for, try enabling the "allow_envelope_sender" option in config.inc.php and then set the "Bounce Address" setting on Journal Setup, page 1. (Your mail server may not allow you to do set this second option.)
To enable or disable self-registration of various roles, see Journal Setup, page 4, under "User Registration".
Open Journal Systems Team
Don't miss the First International PKP Scholarly Publishing Conference
July 11 - 13, 2007, Vancouver, BC, Canada