Question: how to create rule in outlook 2016 for specific domain?
Answer: Outlook 2010/2013/2016/2019: File > Info > Manage Rules and Alerts > E-mail Rules tab. ... 
Click New Rule to open the Rules Wizard.
In the Start from a blank rule section, choose Apply rule to messages I receive and click Next.
Under Step 1: Choose Condition, choose with specific words in the message header.