I have Employee Directory which shows all employees, rooms etc. but I want to have in my search results only people from "specific domain: mydomain.com". How I can do that?
Can you define your "domain" in another way? The reason I ask is out of the box you can do suffix wildcard so you can't do "workemail:*.mydomain.com". But if you use the Company field in AD, you could sync the company field to the user profile and the provide a refiner for the Company field.
Many times with SharePoint you have to find alternative approaches to the specific solution you seek, this is a good example.