"Host Unreachable" error

[chesneyj]

My office runs Exchange Server 5.5 on an NT 4.0 Server. For the last week, I have noticed that e-mails to one particular domain address are not getting out. I have contacted the host company for this site but they said that we are not blocked by them in any way. E-mail sent from this address can come in to users but e-mail sent out to the address doesn't work. The error simply says "host unreachable".

I have looked at Microsoft's KB but nothing there seems useful. I have stopped and started the services as well as rebooted the server. No new software has been installed and nothing has changed in the configuration of the machine.

Any ideas?

Thanks. Brenda Sherrod
Network Administrator
Alliance Architects, Inc.

 

[dneisler]

Can you ping their mail server? If you don't know what the mail server's name is, you can look it up using NSLOOKUP (if you need help with that let me know).

It sounds more like a routing issue than an Exchange issue to me.

 

[zoeythecat]

I get those messages all the time in my IMS queue. It is just incorrect email addresses (in my case anyway). Can you confirm that the "Host Unreachable" is the correct email address? To test, if you are on another network (Like your home network) just send a test email to that exact email address and see if it bounces back on you.

 

[JohnHarrington]

Do you host any web sites? I ask because we host several, and one client in particular wasn't getting any of our messages, though we received their just fine (testing from home to the same address was successful). What I did was add a record for their mail server (did a tracert to find the IP), in the HOSTS file on the mail server. Haven't had a problem since...

 

[chesneyj]

An update:

I finally got some answers from the company hosting the e-mail addresses. Apparently, some updates were done on their incoming e-mail server a little over a week ago (the same time I began having problems). It turned out that the updates made it impossible for the e-mail server to accept mail from Exchange Servers with an "_" in their name, which my server does. I noticed that another domain name was not getting our e-mails either. Sure enough, they are hosted by the same company. Now, we have to wait for them to fix the problem.

Thanks for all of your help and suggestions. Brenda Sherrod
Network Administrator
Alliance Architects, Inc.