How do I setup no-reply@mynet.com on Exchange 2016?

Exchange 2016 CU9 DAG 2 Node on Windows 2016 Datacenter servers both are on VM's ESXi 6.5 hosts.

Getting this event

Log Name:      Application
Source:        MSExchangeTransport
Date:          7/16/2018 10:00:25 PM
Event ID:      1025
Task Category: SmtpReceive
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      SERV021-N1.mynet.com
Description:
SMTP rejected a (P1) mail from 'no-reply@mynet.com' with 'Client Proxy SERV021-N1' connector and the user authenticated as 'SQL Admin'. The Active Directory lookup for the sender address returned validation errors. Object not found
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="MSExchangeTransport" />
    <EventID Qualifiers="49156">1025</EventID>
    <Level>2</Level>
    <Task>1</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2018-07-17T02:00:25.179316800Z" />
    <EventRecordID>459691</EventRecordID>
    <Channel>Application</Channel>
    <Computer>SERV021-N1.mynet.com</Computer>
    <Security />
  </System>
  <EventData>
    <Data>no-reply@tgcsnet.com</Data>
    <Data>Client Proxy SERV021-N1</Data>
    <Data>SQL Admin</Data>
    <Data>P1</Data>
    <Data>Object not found</Data>
  </EventData>
</Event>


How do I setup no-reply@mynet.com on Exchange 2016?

I moved from Exchange 2010 today which this was setup on and worked great  Nee help on 2016 for this.

Is this a send only account ?  How do I set that up?  I saw an article saying create a send only account and setup a transport rule.  

I do not remember doing that on Exchange 2010

Thank you in advance

Tom