Can't send mail to certain domains

[dfortin]

So I have a windows 2k3 sp1 server running Exchnage 2k3 sp2.

2 domain controllers (2k3 and 2k), each of which are dns servers. I have MX records setup correctly on each dns server for the internal Exchange server.

I can receive mail just fine.
I can send mail to 95% to all attempted domains, but a few I simply cannot send to.

I can resolve the underliverable domains on both the dns servers and the exchange server. I can even telnet to port 25 on the undeliverable domains from the exchange server!

Everytime I get a bounce back it says:

Your message did not reach some or all of the intended recipients.

Subject: testing
Sent: 1/20/2006 12:35 PM
The following recipient(s) could not be reached:
'xxx@xxx.com' on 1/20/2006 12:35 PM

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.

<xxx.xxx.com #5.5.0 smtp;550 xxx@xxx.com>: Sender address rejected: Access Denied

On the exchange server I am also getting an smtpsvc Event ID (2021) warning telling me that it is not able to contact the dns server, but I can ping the dns server as well as do nslookups against it.

Does anyone have an idea of what is going on here?

thanks!

 

[nsantin]

Do your mail servers have revDNS entries?

 

[u080570]

I think nsantin is right - you need to have external DNS set up.

From your Exch Mgr, go to your Default SMTP Virtual Server, right click, select Properties

Click the Delivery tab
Click the Advanced button
Click the Configure button (for external DNS)
Add your external DNS servers....
Stop/Restart your Default SMTP Virtual Server

If this doesnt fix your issue - is there any chance the sites you are trying to send to have some kind of SPAM blocker set up that is blocking you?

 

[nsantin]

Actually I said do you have a reverse DNS entry for your mail server IP. Goto dnsreport.com and test your domain.

A lot of domains will not accept mail unless your mailserver has a reverse DNS record. If you can't setup a RevDNS, (ie DHCP Address) then setup your ISP MailServer has a bridgehead.

 

[dfortin]

nsantin you are absolutely right. I forgot to create a reverse dns entry for my mail server.

When making the MX record and corresponding A record, I thought my isp name server would do this by default, but they did not.

Thank you very much!