There's a wiki for that.
http://en.wikipedia.org/wiki/Push_e-mail
Push e-mail is used to describe
e-mail systems that provide an always-on capability, in which new e-mail is actively transferred (
pushed) as it arrives by the
mail delivery agent (MDA) (commonly called mail server) to the
mail user agent (MUA), also called the e-mail client. E-mail clients include
smartphones and, less strictly, IMAP personal computer mail applications.