Reverse DNS - Anti Spam Problem..

[blakey2]

Hi,

Recently one of my users told me that she could not email to a specific client.

The rejected error was:

<mailservernetbiosname.mydomain.com.au #5.5.0 smtp;554 Refused. Your reverse DNS entry contains your IP address and a country code.>

I checked my RDNS entries and got the following:

Answer:
aaa.bbb.cc.ddd PTR record: aaa-bbb-cc-ddd.tpgi.com.au. [TTL 86400s] [A=aaa.bbb.cc.ddd]

-----------------------------------------------
WHERE: aaa.bbb.cc.ddd is my static external IP address.

TPG is my ISP (I'm in australia) and the country code of australia is AU.

The client in question has a .com.au domain which is hosted in the US.

Is this causing the issue..?

TPG do not provide/host my nameservers/dns..


There seems to be little google avalaible info on this one..

Thoughts appreciated.

Cheers.

 

[GunnarD]

I'm guessing now.

Because your PTR record contains ip-adress and country-code thet think that this probably is a client machine and not a real mailserver.

 

[blakey2]

Morning GunarD,

Yep. That was my guess too but hoping for a definitive answer.. =)

Cheers.

 

[Guern]

Hi,

Many anti spam measures reject mail from IP's with no reverse dns. Quite a few ISP's now fully poulate their adsl or dial up pools with reverse dns entries in the manner shown above with the IP address listed. These are treated by several anti spam measures as being the same as an entry with no reverse dns as entries with no reverse dns are becoming less common. It's certainly the cause of the problem.

If you cannot get your ISP to change the entry to something like mail.yourdomain.com, then the only alternative is to relay out via your ISP's mail server or another relay service.

Microtech Limited

http://www.mtgsy.net