To get email to flow and not get bounced by spam, we just need to setup a DKIM record. 

• Go into Setup - Admin - Email - DKIM Keys
  https://worldcouncilofcreditunions.lightning.force.com/lightning/setup/EmailDKIMList/home
  
• New Key
• Set the Selectors and Domain
• It'll give you DNS records to add as CName's
• Once the DNS registers, you'll need to click Activate in the admin

YouTube for step by step.
https://www.youtube.com/watch?v=2OmK7bL8Fac