So we got this RSVP card and I'm not sure what I'm supposed to put in the blank...Mr. Lastname and Ms. Maidenname? Is that what the M is for? (And if so, does it matter that we'll be Mr. and Mrs. by the wedding?) The outside of the invite wasn't addressed formally, just with our first and last names together on the same line, so it seems weird to write it like that when the rest of the invite is casual.
I'm not doing formal invites so I know nothing about this and I've never seen it with the M hanging there before.