can't forward mail to sendmail server on same domain

[dampfnudel]

I have a working Exchange 2K server that handles all my email on domain.com. I set up a second mail server running sendmail on RedHat Linux 7.3 so that I can use the Majordomo list server. I set up an Active Directory Contact that should forward emails sent to mylist@domain.com to mylist@sendmail.domain.com.

However, my Exchange server sends back an email saying that "The destination server for this recipient could not be found in Domain Name Service (DNS). Please verify the email address and retry."

I can send messages to sendmail.domain.com from another sendmail instance on the same LAN, so I am assuming the problem is in the Exchange configuration. I have an internal DNS server and I know there is an MX record for sendmail.domain.com.

Thanks in advance for any help

 

[felixfong]

Do you have your internal DNS listed on the top of your prefer DNS??

 

[dampfnudel]

When I do an "ipconfig /all", only my internal DNS shows up. I also did an "nslookup", then "set q=mx" and then entered sendmail.domain.com. Nslookup replied with an MX record that points to sendmail.domain.com, so as far as I can tell, the Exchange server should have the correct DNS settings.

Is there something in Exchange that tells it to handle all email that end with .domain.com, even if the message should go to another server on the same subnet? Do I need an SMTP connector to do this?

 

[tom11011]

does sendmail.domain.com reply with real or lan address?

 

[dampfnudel]

sendmail.domain.com replies with a LAN address. This mail server is not directly exposed to the Internet. My intent is to have mail from the Internet go to the Exchange server and then be forwarded to sendmail.domain.com on the LAN. This technique will let me publish addresses like "mylist@domain.com" instead of "mylist@sendmail.domain.com", but the messages will still get through to the correct mail server.

 

[brontosaurus]

may i ask how you entered the additional DNS records for this "subdomain"?

 

[dampfnudel]

brontosaurus - you're question led me to do some more testing and I was able to resolve the issue. Thanks!

I did some research on the Microsoft Support site and found the following very helpful:

Support WebCast: Microsoft Exchange 2000 Server: DNS Troubleshooting in Transports
May 2, 2002

The solution to my problem: I had an external DNS server configured in my SMTP Virtual Server. This was left over from a previous trouble-shooting session.

By having my ISP's DNS servers defined as external DNS servers, Exchange used these servers instead of my internal DNS to resolve domain names. My ISP has no knowledge of sendmail.domain.com so Exchange could never get the LAN IP address for this server.

Once I removed the external DNS servers from my SMTP Virtual Server, everything worked fine. Exchange asked my internal DNS to resolve sendmail.domain.com first and got an answer and therefore it didn't have to go out to my ISP's DNS. I didn't need any special connectors or settings other than that.

Thanks again