[Exim] Obscure host list bug?

I have just come across what looks like an extremely obscure bug with host
lists in Exim version 3.22. This is not the host list I am using for real
but it illustrates the problem:

host_reject_recipients = ! *.gov.uk : *.biz

As I understand it, the above should accept hosts in gov.uk and otherwise
go on to reject hosts which match *.biz. (My real host list is much more
complicated than this and the ! exceptions are to obviate the need for a
database lookup.)

The following use of exim -bh illustrates the problem:

mailhub1{exim}89: exim -bh 194.61.173.3

**** SMTP testing session as if from host 194.61.173.3
**** Not for real!

>>> host in host_lookup? yes (0.0.0.0/0)
>>> looking up host name for 194.61.173.3
>>> IP address lookup yielded nccms01.lsdteam.co.uk
>>> Alias nccms01.newcastle.gov.uk
>>> Alias nccms01.newcastle-schools.org.uk
>>> Alias nccms01.offshore-suppliers.com
>>> host in host_reject? no (option unset)
>>> host in host_reject_recipients? yes (! *.gov.uk)
LOG: recipients from nccms01.lsdteam.co.uk [194.61.173.3] refused

Note that this IP address has multiple names associated with it, one of
which is in gov.uk. I assume that this is what is causing the confusion.

TYIA.

Richard
--
Richard Gilbert
Corporate Information and Computing Services
University of Sheffield, Sheffield, S10 2TN, UK
Phone: +44 114 222 3028 Fax: +44 114 222 3040