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Configure external DNS for Exchange

After installing Exchange Server, the next step is to configure external DNS for Exchange. It’s important to keep the same namespace internal and external. We will sign in to the public DNS and create the records for Exchange Server. In this article, you will learn how to configure external DNS for Exchange Server.

Information Public DNS Exchange

Important: Read the article Exchange namespace design and planning before going further.

There are three records types that we will add to the public DNS. About the values, you should only enter an IP address for the A record. The MX record is the spam filter, and the CNAME (alias) should point to the DNS name of the A record for the Exchange server. If your IP address changed due to changing Internet Service Providers, you would only need to update the A record.

Note: Always use a spam filter to protect your Exchange Server organization from incoming and outgoing spam. The one we recommend is the SpamBull cloud spam filter.

Record TypeTTLDNS NamePriorityValue

An architecture view of the Exchange namespace is shown below in the diagram.

Create Public DNS records

Sign in to your external DNS registrar. Configure the records.

Configure External DNS Exchange 2016 create public records

Check the Public DNS records

Let’s run the Resolve-DnsName cmdlet to verify the:

  • MX record
  • A record
  • Autodiscover record

Run PowerShell as administrator. Run the Resolve-DnsName cmdlet and the -Server parameter. The -Server parameter will resolve the name against the Google DNS servers. We can check the Public DNS records on the LAN or any external network.

Note: Don’t immediately resolve the external DNS records, as that will not work. The servers around the world have not reflected the changes. Give it a maximum of an hour as the DNS propagation will need time.

Check MX record

Verify the MX record.

PS C:\> Resolve-DnsName -Type MX -Server | Format-Table -AutoSize

Name      Type TTL Section NameExchange     Preference
----      ---- --- ------- ------------     ---------- MX   300 Answer 10 MX   300 Answer 20 MX   300 Answer 30 MX   300 Answer 40

Check A record

Let’s have a look at the public A record.

PS C:\> Resolve-DnsName -Type A -Server | Format-Table -AutoSize
Name           Type TTL Section IPAddress
----           ---- --- ------- --------- A    300 Answer

Check autodiscover record

As of last, let’s check the public autodiscover record.

PS C:\> Resolve-DnsName -Type TXT -Server | Format-Table -AutoSize

Name                   Type  TTL Section NameHost
----                   ----  --- ------- -------- CNAME 300 Answer


You learned how to configure External DNS for Exchange Server. Add the three records to your public DNS and verify that you can resolve the external DNS records. Don’t forget that it can take a little time before you can resolve the DNS.

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ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

This Post Has One Comment

  1. Could you also show the DNS settings for HA with multiple sites? Thank you for a great and informative site!

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