Dr. & Mrs. John Smith
Drs. _______ and ________ Smith
Dr. Mary Smith and Mr. James Doe
When addressing a business envelope where the husband is Mr. and the wife is Dr., the proper way to format the names is to list the titles in alphabetical order. Therefore, you would address the envelope as "Dr. and Mr. [Last Name]." For example: "Dr. and Mr. Smith." This shows respect for both titles.
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.
That would be: "Dr. John and Mrs. Jane Whomsoever".
The envelope should read: Mr. John Doe & Dr. Jane Doe. If you don't know her first name then put: Mr. & Dr. John Doe.
Address on envelope to a doctor: Dr. John Doe is the general form.
If it is a formal letter, "Dr." or "Mrs." should be used.
When address to a doctor it should appear as: Dr. John Doe or John Doe, MD.
I think it would be proper to address the two married PhDs as Drs. John & Jane Doe
Mr. & Mrs. <lastname>
The proper way to address an envelope for a Ph.D. is "Dr. [Full Name]" followed by their address.