Re: Proper ACL condition to block failed rDNS lookup

It can be a PTR, an A/AAAA, an MX, doesn't matter to me. I just want a 
connection coming in to resolve to *something*. If it's just a bare IP 
that doesn't resolve to anything at all then I'll reject that. 
Everything else I'll take care of with other rules.

On 2025-06-08 00:30, Slavko via Exim-users wrote:
> Ahoj,
> 
> Dňa Sat, 7 Jun 2025 23:44:50 -0700 AC via Exim-users
> <[email protected]> napísal:
> 
>> Because according to the documentation that variable is set if it's
>> more than just no rDNS but also a mismatch with a forward DNS query.
>> Unless I'm misreading the below documentation this is not what I'm
>> asking for.
> 
> IMO, the main problem with built-in exim's PTR check is, that it does
> full FCrDNS, thus both of $host_lookup_deferred & $host_lookup_failed
> can refer to DNS problem with both, the PTR or A/AAAA lookup, without
> distinguishing them.
> 
> If one is interested in PTR only, (s)he need to do DNS lookup by self:
> 
>      ${lookup
>      dnsdb{defer_never,retrans_1s,retry_2,ptr=$sender_host_address}}
> 
> Set that into $acl_c_... variable and then check if variable is empty...
> 
> regards
> 


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