[Exim] SMTP authenticator examples?

Hello. I am trying to set up authenticators in exim. Are there
any good examples available? I spent some time searching the mailing
list archives but didn't see anything useful.

I am using Red Hat 7.2 which seems to cause a lot of trouble with
PAM. It built with SUPPORT_PAM=yes so it should be ready to go, once
there are authenticators in the config file.

Thanks,
Mark