Re: [exim] Preventing TXT lookups after successful aclmodif…

Thomas Jacob wrote:

>> I have my own local dnsbl (using wrblnsd). Certainly from the rbl end it
>> appears that Exim does in fact make 2 queries, but the TXT query is
>> unnecessary most of the time (when a lookup returns NXDOMAIN), so unless
>> your lookups are more than say 20% positive, it's hardly going to save much
>> bandwidth - my point being, is it worth the effort anyway ?
>
> My lookups are more like 80%-90% positive, unfortunately. And it's not
> so much about bandwidth but about speeding up acl processing (to reduce
> the number of parallel smtp connections at any one time) and to
> reduce the load on our name servers, at least that's what I hope it will
> do ;-)

Instead of using "dnslists", you could perhaps use the dnsdb lookup type
as a workaround. Example

REVERSE_SENDER_IP =
${sg{$sender_host_address}{\N^(\d+)\.(\d+)\.(\d+)\.(\d+)$\N}{\$4\.\$3\.\$2\.\$1}}

That creates a macro which returns $sender_host_address with the octets
reversed. Then do:

condition = ${lookup
dnsdb{defer_never,REVERSE_SENDER_IP.zen.spamhaus.org}{true}{false}}

This is equivalent to:

dnslists = zen.spamhaus.org

But only does the A record lookup

If you're using more complicated features of "dnslists", it gets trickier.

Mike