[exim] TLS question

I am trying to send email from my server using a Ruby Rails application. The
application uses ActionMailer to send out an authentication email. Even though
the method is supposed to support TLS I am getting issues on my server that is
rejecting the email.

So I am wondering if there is a way to not require TLS for a specific host? I
have tried using host_avoid_tls = my.localhost.com in my transport but it
still seems to deny the connection for my host.

I know the hostname and the ip address of the specific machine that will be
attempting to send the email. Is there anyway possible to make exim accept it
without using TLS?

Thanks,
-Eric