We get on average nine "failed to find sending host name from IP address"
per minute, and many of the rejects are frustrated sendees to our customers.
I'd like to know how to ...
1. permit all sites whose DNS does not reverse into exim regardless of IP
2. block all sites whose DNS does not reverse except for those in an IP net
list
I've experimented with +allow_unknown and net-based policy controls in
chapter 41 as well as removing wildcards from host lists but have not tamed
DNS.
I'm convinced that Exim can do what I want but it's not clear how to do it.
Thanks for your help,
Ned
ps. One strategy that I'd like to try is sorting the failed DNS rejects by
IP, collecting those who have 10 or fewer with the same IP (frustrated
sendees trying to reach us) and putting those IPs into a net_accept list.
Similarly those IPs that sort into large groups are likely to be spammers.
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