I think the radiant mailer extension creates a mail object, which the
actionmailer gem sends. If Actionmailer doesn't write a sent mail
message to the log file ( logger.info "Sent mail to
#{Array(recipients).join(', ')}" ) and there are no subsequent
Net::SMTP errors, it seems like the issue is in how you've configured
the mailer extension. Be sure the field names in the form and the
email page part line up exactly.
You can try inserting some additional debugging in the mailer
extension to see where the failure occurs (http://jeremyhubert.com/
articles/debugging-in-rails.html) and then tail the development log in
another terminal window.