MX Record

Posted on 2006-04-07
Medium Priority
Last Modified: 2010-07-27
Our company changed their name and created another domain name.  We decided to keep both domains active.  I set up the new domain name in exchange to be able to receive mail from the new domain name.  

On the DNS Server, under Forward Lookup Zones, I did see my old domain zone so I created another zone for my new domain.  Inside the new zone, I created a new A record.

My question is, in my old domain I don't see an MX record.  Am I looking in the wrong area?  Should there be one?

Should I create a MX record for the new domain in order to receive mail for the new domain?

I created a MX Record within the domain registered company.  Is this the only place to make an MX Record or should I make another one on DNS even though I don't see an MX Record for my old domain.

Is there a test that I can run on the old domain as well as the new domain to confirm setup for the DNS?  I think that I can use the NSLookup, but I don't know what arguments to enter.

Still, I am not receiving email through the new domain, even though I did the following:

Added the new domain to the recipient policy.
Made sure each user in their mailbox they have two email accounts one with the new domain and one with the old domain.
Created an A record as well as the MX Record with the register for my new domain.
Created a zone and inside the zone created an A record inside the DNS in my domain controller for the new domain.
My new domain now can go to my website.  So my old and new domain have the same public IP address.

But, I still am not recieving email through the new new domain.  What am I missing?

Any Ideas or recommendations are greatly appreciated...

Thank you.
Question by:mtzsw
LVL 24

Expert Comment

ID: 16405999
Chances are you are looking at your internal DNS server and not your external DNS server...

Author Comment

ID: 16406018
Can you explain what is meant by internal and external?

LVL 24

Accepted Solution

flyguybob earned 2000 total points
ID: 16406107
The internal DNS server is likely a domain controller, or other server, which contains the internal DNS records that your systems use in order to resolve names to IP addresses.  If you are looking for an external address, then that internal DNS server should have a forwarder record going to an external DNS server.
The external DNS server provides name to IP resolution(A), IP to name resolution (PTR), mail exchanger name resolution (MX), Sender Policy Framework record resolution (SPF), etc.  This is generally an external server that sits outside of your firewall, or at least allows port 53 in/out.  In the case that your DNS is hosted by your ISPs server, then it is a server at your ISP that provides resolution.

Sometimes this configuration is called split DNS or split-brain DNS.

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LVL 24

Expert Comment

ID: 16406111
AS an example of the external DNS servers for Google.com:

I did a lookup on type NS for Name Server.  If you do it for your domain then you will find the servers that host the external DNS records.  If you don't recognize those server names then chances are you have an external DNS system hosted somewhere.

Expert Comment

ID: 16406456
to configure dns forwarders take properties of your dns server in dns mmc and click on the forwarders tab add the ip address of your isp's dns servers. then go to monitoring tab and select the both checkboxes and test.

you can use nslookup to see the mx record
type nslookup at command prompt then enter
>set type=any (then enter)
>any.domain.com (then enter)
here u can see the mx entries for the mail exchangers
if the machine on which u r launching nslookup is pointed to your internal server then u see the records which u have in your dns.

to receive mail for more than one domain on single public ip you should have mx records in both of your domain records pointing to the same public ip
abc.com. MX IN 86400 mail.abc.com [Preference = 5]
abc.com. MX IN 86400 mail.isp.abc.com [Preference = 10]
mail.abc.com. A IN 86400

xyz.com. MX IN 86400 mail.xyz.com [Preference = 5]
xyz.com. MX IN 86400 mail.isp.xyz.com [Preference = 10]
mail.xyz.com. A IN 86400 (same public ip)

the all other u have set in exchange like recepient policy etc.
LVL 12

Expert Comment

ID: 16406888
Question: is the SMTP server of Exchange accepting the inbound mail connections, or is there any other software in FRONT of your Exchange server handling inbound e-mail? Antivirus/SMTP proxy? An intelligent firewall that can 'see' SMTP-traffic?

<< My question is, in my old domain I don't see an MX record.  Am I looking in the wrong area?  Should there be one? >>
If an external company is hosting your DNS domain, then usually you don't need one. Not for this issue, anyway.

<< Should I create a MX record for the new domain in order to receive mail for the new domain? >>
Yes, with the company hosting your DNS domain, not within your Active Directory domain. Your AD-DNS is usually not authorative.

You can look up the authorative name servers for your domain using http://www.dnsstuff.com/tools/lookup.ch?name=abc.com&type=SOA
Replace abc.com with your own domain name.

<< I created a MX Record within the domain registered company.  Is this the only place to make an MX Record or should I make another one on DNS even though I don't see an MX Record for my old domain. >>
Creating an MX-record on your own DNS is only useful if you have internal hosts performing MX-lookups for your domain (relaying mailservers and the like). Not for inbound Internet mail, no.

First, look up the MX configuration of your 'old' domain. Go to www.dnsstuff.com and use the 'DNS lookup' box and fill out the old domain. Change the type to MX and hit Lookup. Let's say the MX-records point to mx1.disney.com through mx4.disney.com (as is the case for abc.com). Note the MX with the LOWEST preference, and also note the IP address for the mail server. This should correspond to an IP-address of YOUR internet connection.

Do the same thing for your new domain. The name for the MX doesn't need to be the same, but it should point to the same IP-address.

If IP-addresses for MX-records of both domains are the SAME, then we need to look at something in your own network; if they are any different, then the ISP/DNS provider did something wrong.

Please let us know.

Author Comment

ID: 16409787
Part of the problem have been resolved, I can receive email but I can not send email.

If I make the new domain the primary email in the recipient policy, I can receive email but I can not send email.  When I make the old domain the primary email, I can receive and send email.  I can receive email email when people send through the new domain name email address.  Unfortunately, I can not send through the new domain address.

Here's what I did in order to receive email through the new domain, I created a zone and A record within the zone in my internal DNS DC.

The only step that I forgot to do, inside my SMTP virtual server while I created a domain name, I needed to check the property of this domain to allow incoming mail to this domain as well as under the route domain I forgot to forward the mail to the smart host [xxx.x.x..xx] which is the ip of the exchange server, which allow me to receive email.

I am still getting the following error in my www.dnsreport.com test:

WARN Mail server host name in greeting WARNING: One or more of your mailservers is claiming to be a host other than what it really is (the SMTP greeting should be a 3-digit code, followed by a space or a dash, then the host name). If your mailserver sends out E-mail using this domain in its EHLO or HELO, your E-mail might get blocked by anti-spam software. This is also a technical violation of RFC821 4.3 (and RFC2821 4.3.1). Note that the hostname given in the SMTP greeting should have an A record pointing back to the same server.

mail.aerps.com claims to be invalid hostname 'SMTP':
   220 SMTP service ready

I still did not create an MX record in my internal DNS DC, should I create one even though I am still receiving mail.  The old domain doesn't have an MX record within the internal DNS DC.

Also I dont have a cname settup.

The only outstanding issue, is the above error message as well as I can not send email through the new domain name.  

Thank you for all of the follow up .

LVL 24

Expert Comment

ID: 16421331
If you need to recieve the e-mail, then a recipient policy is needed.  However, if you share the namespace with another company, you will not want to check the checkbox that makes the mail primary.  That will lead to potential looping issues if you are not careful.  One of the systems has to be primary for the "other domain".  You will likely also want to put in an SMTP connector and forward mail to the other domain.

More info here:

LVL 24

Expert Comment

ID: 16516824
It's been a few weeks and I wanted to follow-up to see if you got squared away on your original questions and follow-up questions.



Author Comment

ID: 16517531
Thank you for your follow up, Everything is working fine with the exception of the dnsreport issue  but the most important part I can receive and send emails.


LVL 24

Expert Comment

ID: 16517841
That's good that you can send and recieve.
Just make sure that you have an A record, an MX record, and a PTR record on the outside.  ...the PTR may be the only thing that is still missing.  Generally the ISP has to set that up as they own the netblock.  I worked for a large company and we owned a netblock, but our netblock's DNS was managed by MCI and/or AT&T, dependent upon the netblock.  They had to create the PTR (reverse lookup) record for us.

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