iPhone 4S won't let me view read emails

Hey there,

I just recently switched from an Android to an iPhone4S. When I set up my email to sync with the phone everything was fine but it would not download previously viewed messages (read emails that are in the inbox) even though I have it set to download the latest 100. Also, If I read an email on my iphone it marks it as read (as it should) but then 5 or so days later the email is gone from the iphone but it remains in my actual inbox if I log onto gmail via the computer.

I have looked at the settings in gmail as well as the settings in the iPhone and have had no luck whatsoever.

Any help would be great.

PS, It is currently set up as IMAP, I set up another account as a POP that accessed the same email address to see if that would work but it download the very first emails that I ever sent from that email address from years and years ago... So I don't know what that was but POP doesn't;t seem to be working either...

Thanks,

Ian