Thanks Sam and BC.


We aren't using reject-unresolvable-rdns on this particular system.


I wonder if that's what's different about this particular setup? We use it
on most (or even all .. not sure) our other systems.


I think I'll whitelist and blacklist localhost then and see what


Thanks again!




From: spamdyke-users [] On Behalf
Of Sam Clippinger via spamdyke-users
Sent: 10 August 2016 13:42
To: spamdyke users <>
Subject: Re: [spamdyke-users] spam with rDNS resolving to "localhost"


Adding "localhost" to your rDNS blacklist should work exactly as you expect
-- *any* connection that resolves to "localhost" will be blocked.  To allow
connections from the real local host, you could either whitelist
or, if you wanted other filters to remain active for local connections, use
a config-dir to remove "localhost" from the blacklist for


Incidentally, are you using the reject-unresolvable-rdns filter?  That
filter has a special exception for "localhost" to allow that name for but block it for all other IPs.

-- Sam Clippinger





On Aug 9, 2016, at 5:02 AM, Faris Raouf via spamdyke-users
< <> > wrote:

Dear all,


We're having problems with spam being allowed in from IPs with rDNS
resolving to "localhost".

This gets past the reject-empty-rdns filter.


Initially I thought these IPs has no rDNS - using dnsstuff, I get no result
(normally meaning no rDNS). But using host or dig I see the IPs really do
reverse resolve to localhost.



Example log entry:


spamdyke[24468]: ALLOWED from:
<>  to: redac...@redacted.tld origin_ip: origin_rdns: localhost auth: (unknown) encryption: (none)
reason: 250_ok_1470423419_qp_24501




Check rDNS:


# host domain name pointer localhost.



# dig -x


; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6 <<>> -x

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15578

;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0



;  IN      PTR


;; ANSWER SECTION: 21599 IN  PTR     localhost.


;; Query time: 325 msec


;; WHEN: Tue Aug  9 10:41:58 2016

;; MSG SIZE  rcvd: 69





Is figure that it is not safe to add "localhost" in our rdns blacklist file.
Wouldn't our real, local, localhost potentially get blacklisted? 


Any suggestions as to what to do about this would be much appreciated!


Errmm.. in the back of my head there is a dim bell ringing about this issue
and so it might have been discussed before. Sorry if I'm asking something
that's already been covered at some point. Google hasn't helped in this



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