downloadDownload them all to outlookOutlook and sort the emails by size.
Using IMAP should download them (ege.g. headers only) quicker.
If you, don't like me, despise outlookOutlook, then you can use Opera's email imapIMAP client. It works wonderfully with Gmail's IMAP implementation. ( wellWell, not with google appsGoogle Apps, but that's a different story.)