I am developing an App which has a search functionality for user\'s emails with Gmail Account, But I don\'t know exactly how to integrate Gmail account into my app and get t
You may want to look into this website because there is no API from Google to get you're emails. You need to do this through the POP protocol.
http://www.example-code.com/objc/pop3_gmail.asp
then see the features here for the library http://www.chilkatsoft.com/email-features.asp
and download the library here http://www.chilkatsoft.com/downloads_objc.asp
Hope this will get you started with reading emails and listing them, good luck!
as and addition have a look into: https://github.com/mronge/mailcore
and another addition: http://www.etpan.org/
Interesting too: http://code.google.com/p/remail-iphone/