[exim] Exim 4.52 Verify HELO and Verfify reverse_host_lookup…

In my Exim ACL_SMTP_MAIL handler (acl_check_mail) I
have the following warnings set to write to the reject.log,
and get sensible results for many SMTP connections but
for some servers the results seem incorrect:

warn message = X-Greylist: listed no reverse record.

    logwrite = :reject: H=$sender_fullhost: no reverse record.

     !verify = reverse_host_lookup 

warn message = X-Greylist: listed invalid HELO. 
    logwrite = :reject: H=$sender_fullhost: invalid HELO. 
        !verify = helo              

These lines appear in the reject log
(date/time prefix removed to shorten line length):

H=mail.mkcontacts.com [63.65.43.137]: no reverse record.
H=mail.mkcontacts.com [63.65.43.137]: invalid HELO.
H=n10a.bulk.scd.yahoo.com [66.94.237.44]: listed no reverse record.
H=n10a.bulk.scd.yahoo.com [66.94.237.44]: listed invalid HELO.

Will someone please point out my syntax error or misunderstanding?

$ nslookup 66.94.237.44
  Name:    n10a.bulk.scd.yahoo.
  Address:  66.94.237.44

$ nslookup 63.65.43.137
  Name:    mail.mkcontacts.com
  Address:  63.65.43.137

The reverse requests clearly work and the names match as
evidenced by both lookups (later) and the syntax of the
$sender_host_name which did NOT print the HELO string
in parentheses (to indicate the two names matched.)

#These lines appear in the initial main section of the
#exim configuration file:

helo_lookup_domains = *
helo_try_verify_hosts = *
host_lookup = !127.0.0.1/8 : *

--
Herb Martin