Ang gusto mo ba mangyari is to change you old email address to a new one, tapos pag may nag-send sa'yo using your old email address eh ma-foforward sa new email address?
Parang call forwarding sa telepono! Parang malabo ata yun.
Anyway from google support:
If you use Gmail with your Google Account, it's not currently possible to change your Gmail username after you've registered. You can, however, delete Gmail from your account and use a different, non-Gmail address for your Google Account. You can also create another Google Account with a different Gmail username.