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MX Record and Exchange 2003

I have installed Exchange 2003 and need to now forward my MX record so that mail will arrive here.  Here are my questions:

1.  I have opened my firewall to allow for mail.  When I change my MX record with my host provider, do I set it to forward to companyname.com or the external IP address of my router?

2.  Once I have done this will immediately start to flow to Exchange or do I need to use NAT to tell the router to forward the mail to (ie: my local exchange ip)?

3.  How long will it take for my external mail to begin to forward to our exchange server?

1 Solution
You would normatlly point to companyname.com, though the static WAN IP should also work.
At this point mail will immediately be forwarded to your Exchange Server.
Sometimes the mx record pointer at the ISP or Web Host takes awhile to update.

If you do not pull the mail down with pop3, it will just sit on the server until the mx pointers kick in.
An MX record cannot be an IP address.
Therefore you will have to create (or get created for you) a host pointed to the external IP address of your firewall/router. The most common format is mail.domain.com

Once that host has been created you can change the MX record to point at that host.
As long as forwarding is working correctly, mail will start to come in as soon as the DNS changes start to propagate. This can take up to 48 hours before they are fully live.
If you have another solution for email on that domain you should keep checking it for at least 60 hours in case of any dns blips on the Internet.


The link to the article below discusses a step by step approach for configuring your MX record. It also contains a lot of other useful information regarding Exchange and connecting to the Internet.

How do I configure and test the MX Record for my Internet Domain name?
Your mx record will point your external IP address ie mail.mycompany.com (is an mx record) and points to

you can verify this by an nslookup ie nslookup mail.mycompany.com and should present to yo an IP thats been allocated by your ISP ie

It takes at least 24 to 48 hrs for the DNS chnages to propagate but if you push for it, it may only take a couple of hours.

After this has been done you don't need to do anything else. Just make sure that port 25 (mail) is forwarded to your mail server's IP address.

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