Information
Select this option to use DNS to route outbound mail. If enabled the connector will use DNS to resolve the IP address of the remote SMTP server.
Rationale:
Basic authentication sends credentials across the network in plaintext. DNS routing helps protect connections from tampering or interception by unauthorized users.
Solution
To implement the recommended state, execute the following PowerShell cmdlet:
Set-SendConnector 'Connection to Contoso.com' -DNSRoutingEnabled $true