[exim] tls_dont_advertise_hosts

The below seems to be working, but I'd like independent confirmation
that it's a good way to exclude a broken host from STARTTLS:
> tls_advertise_hosts =
> ${lookup{$sender_host_address}iplsearch{/etc/exim4/no_tls}{}{*}}

A lot of the people I talk to have broken rDNS. Could / should I go with
EHLO names as well?

Thank you,
--lbruno