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JaxPlanet's avatar
JaxPlanet
Brass Contributor
May 20, 2024

Why is Exchange 2016 using DNS A record instead of MX record to send mail?

Exchange 2016 trying to send mail to sargb.com.

Instead of sending to their MX "sargb-com.mail.protection.outlook.com", it is sending mail to sargb.com (18.235.162.72).

I cleared the DNS cache on the 2-domain controllers and flushed DNS on Exchange.

What should I try next?

TiA!

2016
Exchange Server

1 Reply

  • SournOwl's avatar
    SournOwl
    Brass Contributor
    Aug 01, 2025

    Exchange 2016 defaults to using DNS A records for direct delivery between servers. To force the use of MX records, you need to modify the send connector:

    Set-SendConnector ConnectorName-UseExternalDNSServersEnabled $true -SmartHosts $null
    and ensure that the DNS lookup settings are not checked to use external DNS options.

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