what email program should be installed in order to ar_mailer_rails3 becomes to work?

Question

ar_mailer_rails3 doesn't send emails

bundle exec ar_sendmail_rails3 -e production -v
expired 0 emails from the queue
found 175 emails to send

I think it is possible because email sending isn't setup on server. I installed mail-utils but it doesn't take effect.

Thanks for any help.