exim-users-bounces@??? wrote:
>>>> I have this to block connections with no reverse DNS: # : no
>>>> reverse dns #defer !verify = reverse_host_lookup
>>>> # message = Reverse DNS lookup failed for host
>>>> $sender_host_address
>
>> And rejecting based on missing reverse DNS has way too much false
>> positives.
>
> reverse_host_lookup seems to check if there is reverse DNS and also
> that it has a matching forward DNS. Is there a way to only check for
> reverse and not check that there is a matching forward? All my false
> positives seem to have a reverse DNS but the forward does not match.
>
> Matt
Yes, you can separate the "no rDNS" and the "rDNS/forward mismatch"
conditions. This may be a bit inefficient, but we run caching DNS on our
gateways, so it could be worse. Someone else may have a better way...
;-)
You can obviously use the flags and headers for whatever you want once
you've got them.
regards
Richard
# Check to see if the sending host has a rDNS PTR - never mind whether
# it matches the forward lookup - and log/add header if not.
warn
condition = ${lookup
dnsdb{ptr=$sender_host_address}{false}{true}}
message = X-staffs-no-rdns: true
log_message = There is no reverse DNS on $sender_host_address
# and set a flag - RMR 10.9.07
set ACL_NO_REVERSE_DNS = triggered
# If rDNS exists, check if forward lookup matches. If not, set a flag,
# add a header, and log.
# RMR 26 Nov 2007
warn
condition = ${if eq {$ACL_NO_REVERSE_DNS}{false}}
!verify = reverse_host_lookup
message = X-staffs-rdns-fwd-mismatch: true
log_message = Reverse and forward DNS on $sender_host_address
don't match
set ACL_RDNS_FWD_MISMATCH = triggered
--
Richard Rogers
IT Development and Innovation Manager
Information Services, Staffordshire University
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