HOW DO I TEST AN MX RECORD

[Rustom]

I have an internal DNS server on Windows 2000. What commands can I use from
a command prompt to test that my MX record is functioning properlly.

Thanks

 

[Rustom]

The MX record is on the external DNS server hosted by our ISP, company.com,
however we have a split brain configuration with the same domain name
internally We have internal UNIX server that use Sendmail and point to the
internal DNS server. Email is failing as the unix servers cannot resolve
the MX record for company.com on the internal DNS server. Therefore I
wanted to verify that the Internal MX record is fully operational and how
would I test this.


"Lanwench [MVP - Exchange]"

 

[Enkidu]

You will need at least an A record for the mail server in the internal
DNS, if you want to resolve it by name.. You could have an MX record,
if you wished but that's not absolutely necessary. You could add these
records by hand.

Externally you should have the MX record point at the A record for the
router or firewall and the A record will hold the IP address. Then the
router/firewall should NAT the external address to the internal IP of
the mail server. The router/firewall shouldn't need to know the
hostname of the sendmail server - it has it's IP address. That should
take care of incoming email and no change is required to the internal
DNS. It would do no harm to put the email server's address into the
internal DNS but you will have to do that manually.

The sendmail server should have a default route to the
firewall/router's internal address. It shouldn't need to look up the
internal address in the internal DNS, but it could. You will have to
manually add the gateway's address to the internal DNS if you want its
name in the DNS.

Routing decisions for packets are made on the basis of the IP address
of the required machine, not its name.

You could test your MX record by connecting to the Internet
externally, say through dial up. Then you could drop to a command
prompt and type:

telnet <name of server> 25

If it is working you will get a banner. <name of server> is the name
associated with the MX record. This name will be associated in the MX
record with an A record, which will contain the IP address of your
router/firewall machine.

Cheers,

Cliff

The MX record is on the external DNS server hosted by our ISP, company.com,
however we have a split brain configuration with the same domain name
internally We have internal UNIX server that use Sendmail and point to the
internal DNS server. Email is failing as the unix servers cannot resolve
the MX record for company.com on the internal DNS server. Therefore I
wanted to verify that the Internal MX record is fully operational and how
would I test this.


"Lanwench [MVP - Exchange]"

When you say internal DNS server, do you mean you are hosting your domain's
DNS in-house? That's the only reason you'd need an internal MX record. If
you're not, and you have your own mail server, you don't need an internal MX
record - you're connecting directly to the server.

 

[Matt L]

If you're on a Windows 2000 or Win XP machine, you can
query the mx record by typing the following at a command
prompt:

nslookup

set q=mx
companydomainname

This will return all mail exchanger records for that
domain as well as their preferences. Hope it helps.

Matt L

-----Original Message-----
The MX record is on the external DNS server hosted by our ISP, company.com,
however we have a split brain configuration with the same domain name
internally We have internal UNIX server that use Sendmail and point to the
internal DNS server. Email is failing as the unix servers cannot resolve
the MX record for company.com on the internal DNS server. Therefore I
wanted to verify that the Internal MX record is fully operational and how
would I test this.


"Lanwench [MVP - Exchange]"

When you say internal DNS server, do you mean you are

hosting your
domain's

DNS in-house? That's the only reason you'd need an internal MX record. If
you're not, and you have your own mail server, you

don't need an internal
MX

record - you're connecting directly to the server.

.

 

[Enkidu]

Absolutely, but that doesn't *test* the MX record. It just lists the
DNS entry for it.

Cheers,

Cliff

 

[Lanwench [MVP - Exchange]]

They aren't failing because of an MX record, they're failing because they
can't find your SMTP server. That's an internal DNS problem. Not MX record
related

The MX record is on the external DNS server hosted by our ISP,
company.com, however we have a split brain configuration with the
same domain name internally We have internal UNIX server that use
Sendmail and point to the internal DNS server. Email is failing as
the unix servers cannot resolve the MX record for company.com on the
internal DNS server. Therefore I wanted to verify that the Internal
MX record is fully operational and how would I test this.


"Lanwench [MVP - Exchange]"

When you say internal DNS server, do you mean you are hosting your
domain's DNS in-house? That's the only reason you'd need an internal
MX record. If you're not, and you have your own mail server, you
don't need an internal MX record - you're connecting directly to the
server.