If you're addressing it to both of them - It would be: Mr & Doctor Smith OR Mr & Mrs Smith - depending on how well you know them.
When addressing an envelope to the wife of a doctor who is not a doctor herself then and he is Dr. John Doe, then address the envelope to her as Mrs. John Doe or Ms. (Mrs.) Jane Doe.
Doctor Smith and his wife Reverend Smith (assuming she is using his last name).
The address should read: Drs. John and Jane Doe or, Dr. John Doe and Dr. Jane Doe.
Dr. Mary Smith and Mr. James Doe
Mr & Mrs James Angstrom Jr.
Major and Mrs . . .
Mr. and Dr. Joseph Smith (indicates the wife is the doctor)
You address the husband who isn't a doctor and the wife that is as: Mr. John Smith & Dr. Jane Smith It is protocol that the Mr. comes first and not necessary to put the female doctor's name first.
You write “Dr and Mrs. Smith”
Addressing letter for a husband and wife team:Mr. & Mrs. John DoeDrs. John and Jane DoePastors John and Jane DoeManagers, John and Jane Doe
If it is a formal letter, "Dr." or "Mrs." should be used.
Dear Mr. (name) and Mrs (name)