"Miss Manners’ solution to adjusting the conventional salutation to an age in which women are as likely to be in business as men, is to use ‘Mesdames’ or ‘Dear Madam,’ under the assumption that a well-run business is run by women. If she sends a letter of complaint, she uses ‘Gentlemen’ or ‘Dear Sir.’"
– Miss Manners’ Guide to Excruciatingly Correct Behavior by Judith Martin, published 1983