We're sending out save-the-dates for our wedding by e-mail (it's a pdf attachment). Obviously, for a lot of my friends, I'm also friends with or know their significant others. In other cases, I haven't even met their significant others, and I know that those friends will tell their significant others about the wedding. Should I send the e-mail even to those significant others whom I've never met? The ultimate invitation will include those significant other's names, but what about the electronic save-the date? Any thoughts on this would be appreciated.