For SMTP bits in AD you need the exchange tools. These are for my notes so make sense to me.

Your account needs to be in the enterprise admins and schema admins group.
You need to install the exchange bits so run this command but you also need to mount an exchange ISO. I used Exchange 2019

d:\Setup.exe /IAcceptExchangeServerLicenseTerms_DiagnosticDataON /PrepareAD /OrganizationName:”Contoso Corporation”

We’re not installing or setting up exchange, just need it to put in all the extra exchange stuff in AD for the mailNickname bits

If you don’t need any of the exchange fields you can ignore all this.