Gmail supports IMAP

Gmail is starting to roll this protocol IMAP (Internet Message Access Protocol) out on every device and every platform, for free.
This protocol have a advantage than the previous old supported protocol POP ( supported until now ) , in fact it seem like POP(Post Office Protocol) access, but lacks one critical feature: your changes made on other devices aren't seen in Gmail when you log back in (you must log in again to get changes ).

Official Google Blog :
http://googleblog.blogspot.com/2007/10/free-imap-for-gmail.html