What is the proper salutation to use when writing to a general and his wife?

According to the University of Mary Washington's website, the proper way to address a general is to use is full rank, plus his full name, then a comma, then an abbreviation of his branch of service. As an example: Dear General David MacArthur, USMC

To address both the General and his wife, simply add the abbreviation Mrs. after the General's Rank you would address it as follows

Dear General and Mrs. David MacArthur, USMC

You may see the chart in the related link below: