How to send an email to everyone in the address book? How can I easily send a BCC to everyone in my address book on OS X? 

I need to send everyone my new email address.
Easy - use MailChimp or some other bulk mailing service to get around all the reasons (spam) that mail clients (spam) and mail services make this (spam) hard to accomplish. 

You also might set a vacation auto-reply on the old address and ensure that people get a timely reminder when they email the old.