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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 you go further.

There are three records that we are going to add to the public DNS. With regard to the values, you should only enter an IP address for the A record. The MX record and the CNAME (alias) should point to the DNS name of the A record for the Exchange server. In this way, if your IP address changed due to changing Internet Service Providers, you would only need to update the A record.

Record TypeTTLDNS NamePriorityValue

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

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 make use of the Resolve-DnsName cmdlet to verify the MX record, A record, and the autodiscover record. Run PowerShell as administrator. Make use of 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 on any external network.

Note: Don’t immediately resolve the external DNS records, as that will not work. The changes have not been reflected by the servers around the world. 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 0

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 »

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