You can address an unmarried woman as "Ms." just as well as a married woman. In a situation where you are unsure of the marital status, "Ms." is a safe form of address, and avoid "Miss" and "Mrs."
Mrs. is when a women is married. Ms. is when they are not married. Miss is when thay are younger.
No, it should be Mr. & Mrs. John Doe. You only use 'Ms.' if you are addressing a letter to someone you do not know is married or single or; in these modern times some women prefer you address them as Ms.
In most cases, if you know that a woman is married you would call her Mrs., and if you do not know whether she is married, or if you know that she is not married, you would call her Ms. Also, it is polite to address people as they wish to be addressed, so even a married woman could be addressed as Ms. if that is how she wishes to be known.
If you do not know if the woman is single; married or widowed then you can use 'Ms.' If you know they are single then use 'Miss' or 'Ms.' and 'Mrs.' for married women or widowed women.
American people use the title Ms. to address women, over 18 that are either married or unmarried. Women who are under 18 are addressed as Miss.
You address a woman as Mrs. when you know she is married. When you know she is single you address her as Miss. When you are uncertain about her marital status it is best to address her as Ms.
Mrs. is a title of respect that may be used to address a married woman. Ms. is preferable, especially if you do not know what the woman's preferred title is, or if you do not know the marital status of the woman.
Unless the woman specifies otherwise, always address correspondence to Ms.
'Ms' started with Women's Liberation. It can mean 'Miss' or 'Mrs.' It also comes in handy if you are emailing or sending a letter to a woman that you aren't sure is married or not. If you know the person is married and they are bend out of shape of the fact they are married then put Mrs. 'Ms.' can also be used for younger women.
Miss-for maids, i.e. not married; Mrs - for married women; Ms - when you write a letter or call someone but you don't know whether she is married or not and don't want to be impolite.
Call her ma'am. If written, Ms. Jane Doe is acceptable.
If you are unaware whether a woman is married or not, use Ms. If it is a man, obviously, Mr. is used in all cases. so Ms. for a woman, and Mr. for a man.