[Exim] Known problems with smtp_reserve_hosts?

Hi,
Using exim 3.16, Solaris 7 with security patch cluster.

with sircam being so virilant, our domain has been flooded with smtp
connections, this has had the effect (even though smtp_reserve_hosts is
set to our domain with a mask ... 143.210.0.0/16) of making us hit our
connection max.
Are there any problems here? (such as with the mask parse?)
We've has to increase the max by three times, decrease the per hosts to
2 and we are still having problems!

Here are all the smtp configure entries:

log_smtp_confirmation
smtp_accept_max_per_host = 2
smtp_receive_timeout = 3m
smtp_accept_max = 100
smtp_accept_reserve = 30
smtp_reserve_hosts = 143.210.0.0/16
smtp_accept_queue_per_connection = 70

Any help will be very gratefully received!

Alex