Since your using Exchange 2003 I assume you have an AD domain which lives on DNS. First look at the obvious, can you send mail internally over your network? Are you seeing any other internal DNS symptoms such as slow logons, failed name resolution between client and servers? These items would indicate a problem with your AD DNS structure.

If your internal network is working and your problem is limited to internet mail, start looking at your external DNS. You may want to contact your ISP as there could be problems at their end. Make sure you can see the servers hosting your external domain records and confirm you have an MX record published with your external provider. You haven’t made any changes to your addressing scheme or renamed / added any mail servers have you?

One other thing to think about if you have confirmed internal connectivity and ruled out external DNS as a culprit, is check that your domain has not landed on one or more public blacklists. Blacklisting will cause all sorts of internet mail problems.

Here a couple websites that offer free tools for checking DNS as well as blacklist membership.
http://www.dnsreport.com, http://www.checkdns.net – DNS tools
http://www.spamhaus.org – provides list of various blacklists

Good luck!

You have a DNS Name Server issue.

From your mail I cannot gather your experience level with DNS, so I will give you a long answer. My apologies in advance for going below your knowledge level.

For your domain name you have a registrar. Your registrar will have your domain records which include a name server (NS). Many registrars or even your web site host will provide you free DNS hosting.

So when anybody on the internet types your name, they are first sent to your registrar who then says, this is the NS for your domain. Then your NS will tell the whole internet the IP addresses of all the Hosts that you have listed. Such as your web server, the MX (Mail eXchanger), your OWA, etc.

This, normally, is the broken link. Somewhere either your Name Server is down or the DNS record in your name server is corrupted.

Do a WHOIS search on your domain name. If it is a US domain name like .COM, .NET, etc., go to http://www.internic.net, otherwise go to the respective country’s top level registrar.

Get your NS IP address. Normally there will be a primary and a secondary.

Try and ping your name servers. If that is up, then you need to visit your name server host and look in to the DNS records and see if that exists or is it corrupted, erased etc. You will have to get your DNS record correctly restored, or put a new one in, and get it refreshed. However, remember, the normal refresh period for your DNS records to start getting re-populated on the Internet can be more than 24 hours. So start working fast.

If your name servers are down, contact the ISP hosting the NS immediately.

Another option, is your domain name up and registered ? In case you have contracted it out to some provider and have not renewed your registration, your registrar may have deleted your registration, in which case, the WHOIS will not work and give you a NS.

I hope this helps.

Kind regards

There’s a dns problem somewhere. Probably from outside, but could be somewhere inside as well if you have a firewall and an external host (spam filter) receiving mail. The possibilities are too many to give extensive troubleshooting guideline, but here’s a few.

Check for mx records, make sure they exist. Test from both outside and inside. If you’re having problems getting a response, make sure your domain registration is up to date. Look for a whois server in google and do a search on your domain.

nslookup
set type=mx
your_domain.com

Also, try to see what host is giving the failure in the bounce message. Is it outside your network or inside?

Lirria