Recently I setup an Exchange 2016 Server. Everything looks fine except the Exchange 2016 default Receive connector allows internal relay.
Eg: Two emails eric@abc.com and andrew@abc.com in my domain abc.com. An anonymous user can send emails to andrew@abc.com on behalf of eric@abc.com (no authentication required). But if anonymous user try to send email to jason@condoso.com using eric@abc.com, Exchange will refuse to send it.
May I know how could I do to restrict user authentication even for emails in the internal domain? I cannot disable the Anonymous users otherwise Exchange server will not receive any emails.
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