How to read all mails (read and unread) of GMail account using C#.Net

[libin e t]

Hi,
 
I am designing a web application(ASP.Net) that should read all mails in GMail and create a PST . My first roadblock is how to read all (read and unread) mails. I know, there is an atom feed that will read all the unread mails. Similarly do we have any atom feed or an API that will read all mails of GMail. As per our company policy, IMAP/POP cannot be enabled in my google account. Also, I cannot give direct user id/password since SSO(Single Sign On) enabled. I am able to get the access token using OAuth. Once we have this access token, how can we use this to read all(read/unread) mails from GMail(Inbox, SentItems).
 
I am stuck up in this for a long time. Any help/advice is greatly appreciated.
 
Thanks in advance,
Libin