[exim] Detecting MessageLabs and avoiding

Hi folks.

I'm still having problems with MessageLabs where they reject any email from
me - despite being virus free since Easter and having two MessageLabs
customers plead my case.

For the domains I know use messagelabs I route via our ISP's Smarthost which
works fine. I use a simple file lookup route:

domainlist smarthost_domains = lsearch; /etc/exim/lists/smarthost_domains


smarthost:
driver = manualroute
domains = +smarthost_domains
transport = remote_smtp
route_data = mail.my.isp
no_more


My question is, is there a better / automatic / dynamic way to detect that a
target email domain uses MessageLabs?