We want to create a mailing list for a subset of people based on their relationship status. Is this possible?
It depends what you mean by relationship status, but go to Search - Advanced search and choose "Display results as" - "Related Contacts" and then in the relationships section lower down make your choices. In the search results list there's an Actions dropdown at the top and one of the choices is Group - Add contacts. You can also choose Group - Create smart group if you want the group to keep updated by itself. And then use that Group as your Mailing List.