Alternatively, connect a mail client to your Gmail by IMAP, go to the "All Mail" folder, and sort by size. I just did this with Thunderbird, and it took ~30 mi

Alternatively, connect a mail client to your Gmail by IMAP, go to the "All Mail" folder, and sort by size. I just did this with Thunderbird, and it took ~30 min to download the headers of 33k+ messages.