Learn English – How to address a woman in a letter

feminineforms-of-address

When writing a letter or an e-mail to a man I know the (sur-)name of ("Smith"), I would write:

Dear Mr. Smith,

What should I use when addressing a woman?
Is it (like for married women):

Dear Mrs. Smith,

Or just:

Dear Ms. Smith,

Or:

Dear Miss Smith,

Or even:

Dear Ms./Mrs. Smith,

What is more polite, particularly as I do not know whether she is married (coverture)?

Use Ms., not Ms./Miss

The "Ms." abbreviation was created in large part to avoid the awkwardness of using Mrs./Miss.

I can't speak for all of the English-speaking world, but, in the U.S., Ms. has become the norm.