On Wed, 17 Sep 2003, James Tyson wrote:
An explanation of dnsdb can be found at http://www.exim.org/exim-html-4.20/doc/html/spec_9.html#SECT9.9
Or in the spec.txt file that comes with most Exim packages.
The condition quite simply uses the lookup expansion via dnsdb to look up the a record for $sender_address_domain (ie the domain name of the sender address). If there is a successful lookup it returns the value of the lookup (ie the resolved address) or simply an empty string if the lookup failed (this stops exim throwing an error). It then compares the result with the string "64.94.110.11". If they match it returns true, and thus the ACL declines the message, otherwise false.
Ah yes, I see now. Many thanks. I was wondering about the empty string. Very useful, good work. -- Juha Saarinen