The part of the Business letter which is extra is called the inner second address.
A business letter is known to be as the letter which is regarded as the formal document basically sent from one company to another for official purpose.
Business letter always begin with a salutation and always end with a signature and whose comments are regardless very highly professional in the nature over it.
Therefore Inner address is the extra part of business letter.
Learn more about Business Letter here:
brainly.com/question/1819941
#SPJ2