Set-EmailAddressPolicy

MS TechNet Article on this command

Examples:

1. Update an exiting policy to have different SMTP mailing address rules
   Set-EmailAddressPolicy -id "Company 1"  -EnabledEmailAddressTemplates "SMTP:%g@company1.com","smtp:%g.%s@company1.com"
   • In this example the "Company 1" EAP is updated to have the primary e-mail address set to <first name>@company1.com and a secondary address of <first>.<last name>@company1.com

For more example of the syntax of the filters and e-mail address templates that can be used see the New-EmailAddressPolicy page.