What does the reply to all e-mail function do?

The reply to all e-mail function will generate a reply message to all of the recipients of the message.

Most of the email clients consist of "Reply All" feature which sends your reply to all the people who were included in the thread of original message i.e." From," "To" and "Cc". And it is totally different from the "Reply" feature as this sends your response to that person only who sent you an original message earlier.

It will send a reply message to every entry in your address book.