Re: Unable to sentd email to certain domains...
From: Jim Schwartz (shamusnc_at_poc.earthlink.net)
Date: 07/28/04
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Date: Wed, 28 Jul 2004 00:38:50 GMT
If your domain is
http://www.dnsreport.com/tools/dnsreport.ch?domain=truenorthloghomes.com,
then you need to talk to your DNS provider now.
Think of reverse DNS this way. When you ping a host by name
truenorthloghomes.com, then you get an IP address. When you have an IP
address and want to look up the host name, you are request the name
associated with that IP. Since spammer will often you zombies and other
relays to send mail, they often don't have a reverse DNS set up. You're DNS
provider should be able to set this up no problem.
The hostname not matching is also technically a violation of RFC, I've never
encountered anyone that blocks because the host names don't match.
"Brad Pears" <donotreply@notreal.com> wrote in message
news:eLuvS4BdEHA.244@TK2MSFTNGP12.phx.gbl...
> recently, we had an incident where we were unable to send email to a
> particualr domain. We kept getting NDR's from anything sent to that
domain.
> After calling this comany and talking to their tech support guys, they
> informed me that they had to place our public IP address in their hosts
file
> to resolve the issue and the problem stems from teh fact that they have
> implemented measures to reduce SPAM which involves requiring a reverse DNS
> lookup to be successful from every domain they receive mail from. SInce
ours
> was unsuccessful (due to a problem with our public IP provider), we kept
> getting bounced...
>
> He did mention in an email to me that there was a resolution to this. Can
> someone read this and explain what we may have to do as maybe email to
other
> domains is also not being delivered and we simply do not know about it???
>
> Here is the email that I received from him regarding the problem.
> (Candlelight is our public IP provider.)
> Our public IP is 64.187.12.50
> --------------------------------------------------------------------------
-- > --------------------------- > Thanks for the detailed information. There are two problems: > > The main problem is actually caused by a DNS issue that Candlelight is > > experiencing. 64.187.12.50 resolves to ppp50.candlelight.ca: > > >nslookup 64.187.12.50 > > >Server: ns.surenet.net > > >Address: 216.94.255.3 > > > > > >Name: ppp50.candlelight.ca > > >Address: 64.187.12.50 > > > > > > > > >However ppp50.candlelight.ca does not resolve to 64.187.12.50: > > > > > >nslookup ppp50.candlelight.ca > > >Server: ns.surenet.net > > >Address: 216.94.255.3 > > > > > >*** ns.surenet.net can't find ppp50.candlelight.ca: Non-existent domain > > > > > >Our mail server checks the reverse lookup on the IP address that's > > >connecting, then it checks to ensure that there is a valid forward > > >lookup for the hostname that the reverse lookup resolves to. In this > > >case 64.187.12.50 resolves to ppp50.candlelight.ca but > > >ppp50.candlelight.ca doesn't resolve to anything. This is what is > > >causing the message to bounce. You're probably going to find this a > > >problem sending mail to a number of different mail servers on the > > >Internet. A lot of mail systems won't do these checks, but they're > > >becoming increasingly common. We recently implemented this check to > > >reduce the amount of SPAM coming into our system. It succeeded in > > >reducing spam by 60-75% and has only caused 3 complaints from > > >legitimate users (you being one of them). As a temporary fix, I've > > >added a entry in the host file of our mail server pointing 64.187.12.50 > > >to ppp50.candlelight.ca. This will fix the problem for mail entering > > >SureNet but you'll have a similar problem with other mail systems. > > > > > >The second problem is that the hostname of your mail server > > >(true3.tnlhdom.local) is not a valid domain name. While this shouldn't > > >cause a direct problem with SureNet's mail system, you may find that a > > >few mail systems on the Internet will reject your mail for this reason. > > > > > >I'd recommend setting your mail server up as what is called either a > > >Smart Host or a Blind Host which would mean relaying your mail through > > >either mail.surenet.net or mail.candlelight.ca. > > -------------------------------------------------------------------------- -- > ------------------------------------ > > WHat is he referring to with Blind host or Smart Host? Is it a good or bad > idea to do what he suggests? ALso we will be moving our DNS over to this > company from where it is now in the next few months.... > > Also, the domain name of true3.tnlhdom.local is what is on the NDR that we > get when we are bounced. This is the local name for our exchange server. Our > actual domain name is truenorthloghomes.com. Do I need to configure > anything differently in the DNS area?? > > > > Any help with the above would be moset appreciated... > > Thanks, > > Brad > > > >
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