If the process inside spawn fails

Hi
    I have used spawn pluggin successfully in my test rails project(will
use in original) for spawning process
http://rubyforge.org/projects/spawn/

My controller code as below
class UserController < ApplicationController
def create
t=spawn do
  sending_mail_function(@user)
end

def sending_mail_function(user)
d=LateNotice.deliver_late_timesheet(user)
end

end
end

LateNotice is classs derived from action mailer..My question is suppose
sending mail function failured how can I track that?Just for example
after clicking mail send button i ahve to send 3 mails to a particular
user. I am disconnecting the LAN cable(just for example)..So in that
case also a new spawn id is returned and the execution after spawn will
continue..But actually mail not send..How can I track this in above

Sijo