The correct way to address an envelope to a married couple that have different last names is to use both of their names. For example, you could write Mr. Johnson and Miss or Ms. Dwyer.
Married or not , this person may be rightly addressed as Dr.
Dear Mr. (name) and Mrs (name)
Address it as 'Pastor---(the name of the pastor).
Same as to anybody else. Put the name and address of the person clearly in the center of the envelope.
You may say to Signore & Signora or abbreviate it as Sr. & Sra.
You can address it to only one, or address it to both using both names. Either way is acceptable.
"Mr. & Mrs. C. Smith" if you know his first initial. If not, then "Mr. & Mrs. Smith" would be correct.
* Senor & Senora ____________________. Senorita is single, Senora is married.
Dr. John Smith Dr. Mary Brown if they are at the same address, of different genders and not married. Dr. John Smith & Dr. Mary Brown if they are at the same address and married but not using the same last name. Drs. John & Mary Smith if they are married and using the same last name Dr. John Smith Dr, Fred Brown if they are at the same address of the same gender and not married. The progression is the same as above if they are married.
In this wonderful modern age you can simply write her name on the envelope. It doesn't need to label her as married, unmarried, engaged, solo, etc. For example: If the person's name is Giselle Renoir and you want to invite her to a party then simply address the envelope to Giselle Renoir at her address. If you want to invite her husband too then simply address it to Giselle and Pierre Renoir.
When addressing an envelope to a recent widow, it is customary to write the person's name starting with the title "Mrs.". Just because a woman is a widow does not mean that a woman is not still married.
Dr. [Husband's Full Name] and Dr. [Wife's Full Name]