I recently upgraded to iOS7 on my iPhone 4s. My pop mail account is downloading all of the emails on my server instead of allowing me to specify how many I want to see. How do I set that now?

I now have 12,000 unread messages on my iPhone 4s. it used to be that i could specify how many it would download. That option seems to be missing. I tried edit the emails, selecting them all and then marking them as read. Their status updated (no blue dot), but the mail app still lists those emails as unread. It's a little disorienting to see a red number on my mail app indicating i have over 12,000 unread emails. Any help would be appreciated.