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Reverse DNS lookup failed

Created: 21 Apr 2009 • Updated: 21 May 2010 | 5 comments

Hello,

Since this morning, for some emails that are being sent out from our office (exchange 2007 to brightmail appliance) we get this bounce back:

#< #5.0.0 smtp; 550 Host-Lookup-Failed: Reverse DNS lookup failed for 212.178.133.166 (failed)> #SMTP#

the .166 ip is our brightmail gateway and if i look in the message audit logs of the gateway i see this:  Message rejected by MTA.

Any idea?
The mx records are set correct to the .166 IP so i dont understand why most mails deliver fine but some get this msg suddenly.

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KevK76's picture

What about your ptr records Michiel?  Why don't you send me your domain name, you can also try some online tools to help resolve the issue:

http://www.howismydns.com/tools.php

Cheers,

Kevin

 

 

 

 

MichielB's picture

I PM'd you the domain name, but here you go: techconnect.nl
we dont have any PTR records set, in fact i cant set PTR myself anyway, why is that needed suddenly? before it worked fine.

MichielB's picture

Looks like our PTR record is set wrong, calling our backbone ISP now... sigh, still strange it worked fine before though.

KevK76's picture

Hi Michiel,

You told us how your delivery binding settings looked after you made changes yesterday but you didn't mention what the values were originally pointing to. 

Before you made changes yesterday was your 'Non-local messages' delivery binding set to '.167'? 

If you change the setting back to what it originally was does it resolve the problem with the issues?  

I suppose you can look into this if correcting the ptr records doesn't work, but I expect that should resolve the issue.

Cheers,

Kevin

MichielB's picture

It looks like after changing the PTR on the 166 IP it works..... so far,
and yes it used to be .167 before in the non local.

Thanks for your help.