[exim] Slow mail sending from Windows XP

We've just noticed that sending email from Windows XP boxes was going
slow. There was a three second delay on connecting to exim before the
welcome banner appeared.

The problem seems to be that Windows XP firewall now quietly drops
RFC1413 requests (or at least not answer them very quickly) whereas it
used to reject them.

I've had to put "rfc1413_hosts=!*" into my config files to get the speed
back up. The default for this option is to test every host.

Jon.