How can I add the email addresses of everyone who has ever written to me to my address book all at once?

You cannot do it all at once. Inbox Open any email, after the "From....(email address) if there is a small green +, you do not have that contact, so click on the green + Fill in the rest of the information If there is a yellow "Save" on the top right, select it, otherwise the data won't be kept. Also, it takes a little time for the info to be saved. You might just want to sort those contacts - from Contacts" page, Select "Add Category" Then, as you add a contact, you can add them to a particular category. Since you will be watching for the little green +, going from one email to another is not too bad. Good luck