DEAR MISS MANNERS: Suppose Miss Jones marries Mr. Smith and decides, for whatever reason, to retain her maiden name. She is still deserving of the married honorific, is she not?
Is "Mr. Smith and Mrs. Jones," therefore, the proper form to put on an envelope, to be followed by street address, city and state?
GENTLE READER: Deserving? “Deserving”?
Miss Manners chooses to believe that you only made an unfortunate word choice, not that you believe that it is an honor for a lady to be married, and that the title “Mrs.” reflects that.
But then why do you not accept the fact that this problem was solved with the 20th-century revival of the 16th-century title “Ms.”? It is an abbreviation of the honorific “Mistress,” which was the respectable equivalent of “Mister,” to be used regardless of marital status. "Ms." long predates the more restrictive abbreviations “Mrs.” and “Miss.”
So it is "Ms. Jones and Mr. Smith."
Also, you forgot the ZIP code.