The Distribution List All Users is a dynamic distribution list based on users with @royalelect.com email boxes so Contacts cannot be added since they don't have mailboxes.
- Create a new Contact
- Go into Exchange Admin Center
- Go into Mail Flow
- Create a new rule
- Give the rule a name
- In the Do the following select Bcc the message to
- Choose the contact you created, click add and then ok
- Click more options
- Under Apply this rule if, scroll to The Message
- Select To or CC box contains this person
- Select the Dynamic Distribution List and click add, then ok
- Finally click Save